Comissão Internacional de Grandes Barragens (CIGB

Comissão Internacional de Grandes Barragens (CIGB-ICOLD)
83ª Reunião Anual – Stavanger – Noruega
Reunião do Comitê técnico de conscientização pública e educação
Committee on the public awareness and education (COPAE)
Chairman: Peter Mulvihill, Nova Zelândia; Vice-Chairman: José Polimón, Espanha
Países participantes do COPAE:
Alemanha - Brasil - Canadá - China - Espanha - Estados Unidos da América - França - Índia - Irã Itália - Japão - Noruega - Nova Zelândia - Reino Unido - Rússia - Sri Lanka - Suécia
RELATÓRIO DE PARTICIPAÇÃO DO REPRESENTANTE DO CBDB
Tem o presente a finalidade de registrar a participação de representante do Comitê
Brasileiro de Barragens na reunião do Comitê técnico de conscientização pública e
educação da ICOLD (COPAE) realizada em 14/06/2015, dentro da programação da 83ª
Reunião Anual da ICOLD, que teve lugar na cidade de Stavanger, Noruega.
Este comitê técnico tem por objeto desenvolver o relacionamento da ICOLD com
os meios de comunicação em geral, bem como tratar dos assuntos relacionados à
organização da memória técnica da ICOLD, sua sistematização e explicitação por meio de
publicações e uso de mídias que tornam acessíveis aos técnicos e ao público em geral
conhecimentos sobre recursos hídricos, barragens e outros temas correlatos.
Um dos principais trabalhos realizados pelo COPAE é o de revisão e de atualização
do Plano de Comunicação e Estratégia da ICOLD 2000; detalhes no Termo de Referência
do COPAE no link (área restrita para membros da ICOLD) http://www.icoldcigb.org/GB/Members_section/technical_committees.asp.
A agenda da reunião, realizada das 9h às 13h, que foi presidida pelo Chairman Peter
Mulvihill (Nova Zelândia), teve como temas: introdução, revisão da composição do comitê,
apresentação de novos representantes, revisão da agenda da reunião, comentários sobre a
ata da reunião anterior (Bali), debate sobre o artigo “Superação de custos de construção e
infraestrutura elétrica: uma barreira instransponível?” (“Construction costs overrun and electricity
infrastructure: an unavoidable barrier?”, B.K. Sovacool, Ph.D, Aarhus Universitet, Danmark),
atualização sobre atividades de mídia e conferências de imprensa, estratégias de
conscientização do público sobre barragens e reservatórios, relato das atividades de cada
comitê nacional, projeto de produção de vídeo-documentário institucional da CIGBICOLD, disponibilidade de apresentações em PowerPoint (e pdf) no site da ICOLD (“share
space”, no link dos comitês técnicos da ICOLD em referência), publicação do Plano de
Comunicação e Gerenciamento de Mídia para Comitês Nacionais, Termo de Referência
COPAE 2015 – 2018, discussões sobre questões atuais e planos de trabalhos futuros,
distribuição de tarefas.
No que se refere aos relatos das atividades dos comitês nacionais, fizeram breves
exposições os representantes da República Tcheca, dos Estados Unidos da América, do
Japão (distribuiu a publicação “Dams in Japan – Overwiew 2015”), da Espanha, do Brasil, do
Reino Unido e da Nova Zelândia. Também fez uma breve exposição das atividades
realizadas o assessor de imprensa da ICOLD.
Em sua exposição, o representante do CBDB informou que as participações mais
relevantes do CBDB no cenário nacional brasileiro em 2014 – 2015 se ativeram à Lei de
Segurança de Barragens, às recomendações de interesse público contra a redução da
_______________________________________________________________
Rua Real Grandeza, 219 – Bloco C – Sala 1007 – CEP: 22281-900 – Botafogo – Rio de Janeiro – RJ Tel.: (21) 2528-5320.
Fax: (21) 2528-5959 e-mail: cbdb@cbdb.org.br - http://www.cbdb.org.br CNPJ: 42.334.193/0001-67 Inscrição Municipal 0903.388
capacidade de armazenamento de água e ao acordo de cooperação técnica com a Agência
Nacional de Águas – ANA (em andamento).
Informou também que em 2014 – 2015 o CBDB realizou as seguintes atividades
principais: debates sobre a seca e reservatórios, Registro Nacional de Barragens, IX
Simpósio sobre Pequenas e Médias Centrais Hidrelétricas, XXX Seminário Nacional de
Grandes Barragens, cooperação internacional para formar o Comitê Nacional de Barragens
de Angola, palestras técnicas (concreto, barragens de CCR, construção da UHE Belo Monte,
barragens de aterro e pequenas centrais hidrelétricas), cursos de especialização, 2ª edição da Revista
Brasileira de Engenharia de Barragens, livro “Projeto de usinas hidrelétricas: passo a passo”
e continuação da publicação do informativo bimensal na página do CBDB na internet.
Relatou sucintamente sobre a crise de armazenamento de água no Brasil: menos
chuva, menos água e energia acumuladas, aumento dos custos e sofrimento da população
com esse quadro desfavorável. Ênfase para a situação especial em São Paulo: uma enorme
cidade que está sendo forçada inclusive a usar o volume morto da maior parte de seus
reservatórios porque o volume útil de água deles se esgotou.
Conforme previsto na agenda da reunião, o representante do CBDB fez uma
apresentação em PowerPoint da proposta do CBDB de produção do vídeo-documentário
institucional da ICOLD sobre barragens para divulgação mundial, patrocinado por
empresas do setor, tendo como base o conteúdo do livro “As barragens & a água do
mundo”. Após novas discussões sobre o assunto ficou definido pelo COPAE que o vídeo
deverá, em sua versão inicial, ter uma duração de 3 a 5 minutos. O Chairman do COPAE
se incumbirá de coordenar as ações seguintes, o que inclui a submissão da referida proposta
à apreciação dos órgãos de administração da ICOLD. Ficou combinado que na próxima
reunião do COPAE na África do Sul em 2016 serão avaliados os progressos que venham a
ser alcançados com o projeto.
O Chairman apresentou detalhadamente o documento “Orientação para os
Comitês Nacionais da ICOLD trabalharem com a mídia” (Guideline for ICOLD National
Committees Working with the Media), baseado em uma experiência desse tipo praticada na
Nova Zelândia. Cópia desse documento será encaminhada para conhecimento da Diretoria
do CBDB.
Gramado (RS), 24 de junho de 2015.
Miguel Augusto Zydan Sória
Representante do CBDB no COPAE
_______________________________________________________________
Rua Real Grandeza, 219 – Bloco C – Sala 1007 – CEP: 22281-900 – Botafogo – Rio de Janeiro – RJ Tel.: (21) 2528-5320.
Fax: (21) 2528-5959 e-mail: cbdb@cbdb.org.br - http://www.cbdb.org.br CNPJ: 42.334.193/0001-67 Inscrição Municipal 0903.388
ALGUMAS ANOTAÇÕES SOBRE O CONGRESSO DA ICOLD 2015 – NORUEGA
Miguel Sória
O 25º Congresso da Comissão Internacional de Grandes Barragens –
CIGB/ICOLD foi realizado, juntamente com a 83ª Reunião Anual, na cidade de Stavanger,
Noruega, no período de 13 a 20 de junho de 2015.
De acordo com os anais do conclave (Questions 96, 97, 98, 99 Communications), foram
selecionados 187 trabalhos, distribuídos nas quatro questões: 96 - Inovação e utilização de
barragens e reservatórios (41 trabalhos), 97 – Vertedouros (45 trabalhos), 98 – Aterros e
barragens de rejeitos (41 trabalhos) e 99 - Modernização e reengenharia de barragens
existentes (55 trabalhos). Essa quantidade de trabalhos foi superior à do congresso anterior,
Kyoto em 2012, em que foram apresentados 160 trabalhos, mas inferior ao de Viena em
1991, com seu recorde de 275 trabalhos.
Das sessões de apresentação presencial dos trabalhos da Questão 96 – Inovação e
utilização de barragens e reservatórios - nos chamaram a atenção dois deles, que de alguma
forma estão relacionados ou são relacionáveis com a realidade brasileira, que julgamos
serem dignos de nota, como explanaremos na sequência.
Barragens no mar
Segundo o Relatório Geral da Questão 96 (Luc DEROO, França), item 4.10
Barragens no mar (p. 184 da versão em inglês), “... o mar pode ser utilizado para criar
reservatórios...”.
O autor do relatório aponta como suporte para tal afirmação o conteúdo de dois
trabalhos, sendo que um deles, intitulado “Novas soluções promissoras para a energia das
marés” (New promising solutions for tidal energy), elaborado por F. Lemperiere, N. Nerincx e C.
Bessiere (França) apresenta novidades tecnológicas quanto ao aproveitamento das marés
para a produção de eletricidade. Basicamente, os autores, reconhecendo a baixa eficiência
das soluções desenvolvidas até então nesse campo, propõem como inovação o emprego de
uma combinação de lagoas artificiais e canais com turbinas submersas (in-stream), em locais
específicos na costa, formando algo como “Parques Maremotrizes” (Tidal Gardens),
similares aos parques eólicos. Estimam eles que essa solução, se adotada globalmente,
poderá produzir por volta de 1.500 TWh /ano em 20 países, incluído o Brasil, mesmo com
as variações das marés naturais tão baixas quanto 3 ou 4 metros.
Avaliam os autores que o Brasil tem condições parecidas com as da China: costas
longas, reduzida profundidade do mar e bastante baixa amplitude das marés. As
possibilidades aparecem essencialmente ao longo de mil quilômetros no litoral norte a oeste
de São Luís - MA, onde a amplitude da maré é de cerca de 3 metros. Nessas condições, o
suprimento de 50 a 100 TWh / ano parece uma meta razoável, segundo afirmam.
Pesquisando sobre esse assunto, no que concerne especificamente ao Brasil,
excetuando os projetos de pesquisa da COPPE-UFRJ sobre energia que vem do mar, as
demais informações obtidas não foram nada animadoras.
Como exemplo, citamos o Plano Nacional de Energia PNE - 2030, Caderno 9,
Outras Fontes, em que é apresentada uma detalhada avaliação do potencial brasileiro da
energia do mar (marés, correntes marinhas e ondas), bem como dos impactos ambientais que
causa. Todavia, o item 3.3.2 (p. 178 e 179) desse documento, a guisa de conclusão, registra
que “...Com a tecnologia atual, a exploração econômica da energia potencial das marés só se justifica para
amplitudes superiores a 5 metros. Existem poucos locais no mundo onde se verifica tamanha mudança nas
marés. As marés de maior amplitude no mundo estão localizadas no Canadá, Reino Unido, França,
Argentina e Rússia (INETI, 2001). No Brasil, as marés de maior amplitude ocorrem no litoral
maranhense. Na baía de São Marcos, chegam a superar 5m nas épocas de sizígia*....” (*Sizígia: conjunção ou
oposição de um planeta, especialmente da Lua, com o Sol).
17/07/2015
Página 1
ALGUMAS ANOTAÇÕES SOBRE O CONGRESSO DA ICOLD 2015 – NORUEGA
Miguel Sória
Confirmando essa tendência minimalista, a Agência Nacional de Energia Elétrica
(ANEEL) faz constar em seu Banco de Informações da Geração somente um
empreendimento de fonte maré, com potência associada de 50 kW, cuja construção não foi
iniciada. E o Balanço Energético Nacional - BEN 2015 (ano base 2014) e o Plano Decenal
de Expansão de Energia PDE 2023 sequer mencionam algo sobre energia de marés no
Brasil.
Ou seja, a insuficiente amplitude das marés que ocorrem nas costas brasileiras, que
são incompatíveis com o uso das tecnologias atualmente conhecidas, explica com
razoabilidade o motivo pelo qual permanece inexplorada essa fonte energética em nosso
país.
Contudo, os novos argumentos produzidos pelo estudo francês talvez mereçam ser
técnica e economicamente avaliados no Brasil porque prescrevem uma redução de 5 para 3
metros das amplitudes mínimas das marés necessárias à produção de energia elétrica, que é
uma exigência técnica aparentemente mais compatível com o regime de marés de nossas
costas marítimas, principalmente as localizadas na porção setentrional do país.
Desse modo, esta anotação tem por objetivo principal suscitar o debate geral sobre
o assunto, já que há uma inovação em curso com potencial de mudar o estado da arte da
construção de usinas no mar, o que, se concretizado e eventualmente aplicado em nosso
país, poderá diversificar e robustecer ainda mais a nossa matriz energética.
Como medida prática, sugerimos que o assunto seja levado inicialmente ao
conhecimento da Comissão Técnica Nacional de Pesquisa, Desenvolvimento e Inovação
Técnica do Comitê Brasileiro de Barragens – CBDB, de modo que esse colegiado avalie a
proposta, eventualmente a encaminhe para análise também de outras comissões técnicas do
CBDB e ou também de instituições externas. Na hipótese das análises serem
eventualmente feitas, o intuito é de que se avalie a viabilidade de elaboração de um
documento técnico conclusivo que possa ser levado à apreciação das autoridades
competentes do país.
Anexo:
LEMPERIERE, F., NERINCX, N. and BESSIERE, C. (France). New promising
solutions for tidal energy. Stavanger, Norway. CIGB-ICOLD Congress, 2015 (Q.96,
R.36). 18 p.
Fontes citadas:
COPPE-UFRJ sobre energia que vem do mar
[http://www.coppenario20.coppe.ufrj.br/?cat=20]
Plano Nacional de Energia PNE - 2030, Caderno 9, Outras Fontes
[http://epe.gov.br/PNE/20080512_9.pdf]
Agência Nacional de Energia Elétrica (ANEEL) - Banco de Informações da Geração
[http://www.aneel.gov.br/aplicacoes/capacidadebrasil/FontesEnergia.asp?]
Balanço Energético Nacional - BEN 2015 (ano base 2014)
[https://ben.epe.gov.br/downloads/Relatorio_Final_BEN_2015.pdf]
Plano Decenal de Expansão de Energia PDE 2023
[http://epe.gov.br/PDEE/Relat%C3%B3rio%20Final%20do%20PDE%202023.pdf]
17/07/2015
Página 2
ALGUMAS ANOTAÇÕES SOBRE O CONGRESSO DA ICOLD 2015 – NORUEGA
Miguel Sória
Usinas reversíveis apoiadas por fontes alternativas
De acordo com o Relatório Geral da Questão 96 (Luc DEROO, França), item 3.2
Encontrar otimizações ou novas soluções para armazenar energia (p. 676 da versão em inglês),
o rápido crescimento de fontes intermitentes de energia (eólica, solar) na Europa no início
do século 21 produziu um ambiente favorável para o desenvolvimento de centrais de
armazenamento bombeado (Pumped Storage Project - PSP), embora reconheça que persistem
fatores que impedem esse desenvolvimento e que retardam investimentos, que levaram os
estados europeus a não estabelecerem mecanismo para valorizar os serviços de rede
prestados pelas PSPs.
No entanto, o trabalho intitulado “Projetos de armazenamento por bombeamento
entre reservatórios existentes na Espanha pela Gas Natural Fenosa - GNF” (Pumped storage
projects between existing reservoirs in Spain by Gas Natural Fenosa), elaborado por Javier Bastan,
Nuria Rodriguez e Ana Martín (Espanha), apresenta um relato sobre o desenvolvimento de
projetos da GNF de armazenamento por bombeamento a partir de barragens existentes e
seus reservatórios para armazenar a energia potencial produzida a partir de outras fontes,
como o vento ou a solar, e, posteriormente, turbinando a água para obter energia elétrica
quando necessário. Três dos novos projetos, Belesar III, Salas-Conchas y Edrada, se
localizam no noroeste da Espanha.
Conforme ressaltou uma das autoras durante a apresentação, esses projetos
permitirão armazenar principalmente a energia produzida a partir do vento, nos momentos
em que, devido à redução de demanda - o que ocorre frequentemente no período noturno
na Espanha -, é difícil utilizá-la na rede elétrica ou integrá-la no sistema de energia.
Portanto, as principais razões para usar os reservatórios existentes em um esquema
de bombeamento de água entre eles são: otimizar os custos, evitar impactos ambientais e
sociais, otimizar o uso de barragens e reservatórios existentes, integrando-os com outras
fontes, inclusive as intermitentes.
Embora essa alternativa seja conhecida no meio técnico brasileiro, o Plano
Nacional de Energia PNE - 2030, Caderno 3, Geração Hidrelétrica, menciona no item 2.5
Usinas reversíveis (p. 108 a 110) que praticamente inexistem usinas reversíveis no Brasil
porque as hidrelétricas construídas foram dimensionadas para atender a demanda na ponta.
No entanto, não descarta o uso de usinas reversíveis no aproveitamento do potencial
hidrelétrico da Região Amazônica.
O estímulo que nos faz refletir sobre esse tema adveio justamente da citada
complementaridade entre as fontes hidráulica e eólica praticada pelos espanhóis, porém,
conferindo a esse conceito um novo viés, o da “conservação global” da energia, pelo que se
daria utilidade à energia eólica ou solar que seria irremediavelmente desperdiçada por
eventual insuficiência de demanda. Analogamente, utilizando um conhecido jargão do setor
elétrico, dir-se-ia então que se deixaria de desperdiçar uma “energia vertida turbinável”, ou
seja, aquela energia desaproveitada devido à existência de fatores sistêmicos incontornáveis.
Assim colocados os elementos, por esta anotação nos parece adequado sugerir que
seja investigado, no presente momento, quais são as condições e quais são as possibilidades
do nosso sistema interligado no que se refere a investimentos em usinas reversíveis,
aproveitando esse tipo de complementaridade entre fontes de geração de energia elétrica
permanentes e intermitentes, utilizando alguma energia eventualmente “sobrante” no
sistema para bombear água para reservatórios mais elevados, para depois gerar
hidreletricidade quando necessário. Uma forma de “smart grid”.
De igual maneira, como medida prática, sugerimos que o assunto seja levado
inicialmente ao conhecimento da Comissão Técnica Nacional de Pesquisa,
Desenvolvimento e Inovação Técnica do Comitê Brasileiro de Barragens – CBDB, de
17/07/2015
Página 3
ALGUMAS ANOTAÇÕES SOBRE O CONGRESSO DA ICOLD 2015 – NORUEGA
Miguel Sória
modo que esse colegiado avalie a proposta, eventualmente a encaminhe para análise
também de outras comissões técnicas do CBDB ou também de instituições externas. Na
hipótese das análises serem eventualmente feitas, o intuito é de que se avalie a viabilidade
de elaboração de um documento técnico conclusivo que possa ser levado à apreciação das
autoridades competentes do país.
Anexo:
BASTAN, J., RODRIGUEZ, N. and MARTÍN, A. (Spain). Pumped storage projects
between existing reservoirs in Spain by Gas Natural Fenosa. Stavanger, Norway.
CIGB-ICOLD Congress, 2015 (Q.96, R.14). 8 p.
Fontes citadas:
Plano Nacional de Energia PNE - 2030, Caderno 3, Geração Hidrelétrica,
[http://epe.gov.br/PNE/20080512_3.pdf]
17/07/2015
Página 4
Q. 96 – R. 35
COMMISSION INTERNATIONALE
DES GRANDS BARRAGES
------VINGT-CINQUIÈME CONGRÈS
DES GRANDS BARRAGES
Stavanger, Juin 2015
-------
NEW PROMISING SOLUTIONS FOR TIDAL ENERGY (*)
F. LEMPERIERE
HydroCoop
N. NERINCX
ISL
C. BESSIERE
Ingerop
FRANCE
1.
PAST SOLUTIONS FOR TIDAL ENERGY
Hydropower and Tidal Energy have about the same theoretical potential,
above 20 000 TWh/year. The possible energy supply per km2 of tidal basin
(20 GWh/km2 with a tidal range of 5 m) is higher than the average energy supply
per km2 of dam reservoirs (3500 TWh for 350 000 km2, i.e. 10 GWh/km2). Other
conditions are also better for tidal energy: there is no resettlement of population,
monthly and yearly energy are always about the same and the risks from
accidents are low. However Worldwide Hydropower generation is 3500 TWh/year
and Tidal generation is 1 TWh/year.
Environmental impact has been involved for explaining this surprising gap
but the tidal energy impacts seem actually much more acceptable than dams
impacts. In fact the past designs for Tidal Energy have been directly based upon
Hydropower solutions (Tidal Plants) or Wind Farms solutions (In Stream
Turbines). They were poorly adapted to the very specific data of Tidal Energy
and their relevant cost is thus usually too high even for the best sites. This is the
reason of the poor utilization of Tidal Energy.
(*)
Barrages en mer: une solution prometteuse pour l'énergie marémotrice.
467
Q. 96 – R. 35
1.1.
TRADITIONAL TIDAL PLANTS
The usual past solution, as for Hydropower, stores water by dykes in a
reservoir (basin) and uses the corresponding energy through Tidal Plants, i.e.
turbines (usually Bulb Units) placed in a concrete structure. The cost per MWh for
creating tidal basins may be very acceptable but the key problem is the very low
head associated with a good utilization of tidal energy.
The best way for operating a tidal Basin is both ways as per Fig. 2. Power
is obtained 8 hours from 12, the conditions within the basin are similar to the
natural ones but the average head between sea and basin is only about 40% of
the average tidal range hm, i.e. 3 m for exceptional sites and 1,5 or 2 m for most
tidal potential; the flow may be well over 100 000 m3/s for a capacity of some
GW. Heads are thus much lower than for traditional Hydropower and flows much
higher.
The efficiency of hydropower turbines (including bulb units) is very poor for
such heads and the past tidal studies did thus focus on sites of very high natural
tidal range to be operated one way as per Fig. 1. The water volume to be used is
one third of the volume of the Two Ways Solutions (Fig. 2) but the head is about
two thirds of the tidal range hm, i.e. 4 or 5 m for a tidal range of 6 or 7 m. Energy
is supplied only 4 hours from a 12 hours tide and is yearly 2000 hours only of the
rated power. Tidal conditions in the basin are much modified and this may be
unacceptable. The plant structure in open sea is 30 to 40 m high, its civil
engineering expensive. Even in best sites as in the Severn (U.K.) the cost per
MWh remains hardly acceptable with this solution.
Fig. 1
One Way Operation
Exploitation dans un sens
468
Q. 96 – R. 35
Fig. 2
Two ways operation
Exploitation dans les 2 sens
Various studies tried to associate several basins in favourable sites, bulb
units supplying energy full time but this did not increase much the head or reduce
the costs per MWh.
A better solution specifically designed for tidal energy, the orthogonal
turbine studied in Russia, is well adapted to both ways operation under low head
and turbines are quite simple. However the civil engineering is expensive (Fig. 3)
and the power per m of structure is under 500 kW even for high tides. The cost
may be acceptable for some very good sites but too high for most tidal world
potential which is for a tidal range between 3 and 6 m.
Fig. 3
Orthogonal turbine
Turbine orthogonale
469
Q. 96 – R. 35
1.2.
INSTREAM TURBINES
The other basic solution (In-Stream Turbines), tested since a decade, is a
copy of the very successful Wind Farms Solution. The wind speed in many world
places favours wind plants units of 3 to 5 MW onshore and 10 MW offshore. It is
thus likely that within twenty years Wind Energy will equal Hydropower or Nuclear
Energy. Using the same principle and basic design in tidal streams turbines
seems thus attractive and has justified many studies, tests and first years of
operation on some sites. The theoretical potential is significant but there are few
world sites where it is possible to get cost effective energy. A first reason is the
rather low water speed and most designs are limited to units of 1 MW in best
sites. A second reason is that in most best sites the marine conditions of waves,
foundation, maintenance, long electric links increase the cost to a very high level.
Anyway this solution uses only a very small part of the natural energy. The World
Tidal Stream Potential in natural sites seems thus few hundred TWh/year and
less than 100 TWh/year at an acceptable cost.
Similarly the wind energy should have little future if the world wind speed
would be half of the present one and if the only places for wind farms would be
mountains over 3000 m.
With the various solutions studied till now, the cost effective world potential
of tidal energy is very low.
2.
A NEW SOLUTION: THE TIDAL GARDENS (T.G.)
The principle is to create sites where in-stream turbines may operate in
best conditions of cost and efficiency and use a large part of the available
energy.
There are worldwide many places where large basins of hundreds km2 may
be created along shore because the sea depth is less than 25 m and soil
conditions favourable for building dykes within 10 or 20 km from shore. Instead of
using costly traditional tidal plants in the dykes for generating power, the basins
are linked to sea by wide channels in which are placed many in-stream turbines
(Fig. 4 and 5).
470
Q. 96 – R. 35
Fig. 4
Large basin
Grand bassin
Fig. 5
Channel for in-stream turbines
Chenal d’hydroliennes (Maréliennes)
The channels sides are limited by dykes and the bottom lined by concrete.
The channels may be closed by gates similar to gates used with traditional tidal
plants designs. This solution deserves a specific name such as Tidal Gardens or
Tidal Channels (T.G. or T.C.)
Along a six hours half tide the channels, gates are closed when the basin
and sea are at same level and remain then closed one or few hours only; then the
channels are opened and operated at about the same water speed such as 3 or
4 m/s corresponding to the optimal utilisation of in stream turbines. It is possible to
keep this speed full time through adapting the number of operating turbines to the
prevailing water head between sea and basin.
As example, for a mean tide (Fig. 2), the channels are closed along 2 hours then
are all open along 4 hours with the same flow (and water speed). Quite all turbines
are operating along two hours and a part is stopping along the next two hours
according to the reducing water head. The flow is kept the same up to few minutes
471
Q. 96 – R. 35
before an equal level between sea and basin. During spring tides, the channels are
opened 5 hours from six, during neap tides 2 or 3 hours. The flow (and speed of water)
is thus quite the same during all operation. During very low neap tides, some
channels may remain fully closed.
As analysed in 2.4 the cost per MWh of tidal Gardens is much lower than the
cost of traditional Tidal Plants or In Stream Turbines in natural sites.
Beyond cost saving, the impact on environment is also better because the
tidal conditions in the basin and along shore are close to the natural ones (shifted
by 2 hours); high waves and exceptionally high water level are avoided.
Tidal Gardens are a new solution but it is based upon well known
technologies: In-stream Turbines which may be even simplified and large dykes
and caissons at sea. So there is no need of inventing the technologies, which
should be simply optimized and possibly standardized worldwide for huge
quantities.
Contacts have been established with industrial actors, as Electricité de
France, to examine in further details:
(1) the likely hydraulic operation of a schematic “tidal garden site”
(2) the optimisation method of “tidal garden” design criteria such as number
of channels, channel size, dyke track, etc ... .
The hydraulic behavior and the associated design criteria of a “tidal garden”
site depend on:
- the given site configuration : coastline shape, tidal range, sea bottom
geological conditions, possible existing infrastructures,
- power generation objectives : power outputs performance expectations,
ancillary services, intermittency characteristics, storage needs, ...
- socio-environmental needs and conditions : impact on aquatic
ecosystems, impacts on sediment transport and morphology,
opportunities or constraints linked to other uses (navigation, fishing, ...).
2D hydrodynamics numerical modelling of a schematic “tidal garden” site is
under progress to better understand its hydraulic behavior, and meet the above
objectives. Results should be available in the next months and will be soon
published.
2.1.
POTENTIAL PER KM2
A rough evaluation of the Production may be based upon an operation with
a mean tidal range according to Fig. 2.
472
Q. 96 – R. 35
For a basin area S in km2 and a tidal range hm, the likely volume of water
used in an half tide is about, in m3, 0,9 x 106 S hm with an average head close to
0,35 hm. The losses of energy in turbines and channel cannot be known
precisely before detailed studies and tests. An overall loss of one third appears a
reasonable figure. A different value would modify the production but not much the
cost per MWh because the number of turbines is proportional to the expected
production.
The power supply per half tide is in MWh: 106 S x 0,9 Hm x 0,35 Hm x 2 x g
3,600 x 103
3
and should be multiplied by 2 x 705 for evaluating the yearly supply. The direct
result in GWh/km2 is about 0,8 hm2. Some margin should be taken and
evaluations limited to 0,7 hm2.
The necessary generating capacity could be in theory based upon a power
supply over 4000 hours of the rated capacity. It is reasonable for more operating
flexibility to use a figure of 3500 hours and thus a necessary capacity, in MW/km2
of 0,2 hm2 for a yearly production in GWh/km2 of 0,7 hm2.
2.2.
DESIGN BASES
A typical site for Tidal Gardens (Fig. 4) would be a large basin open to the
sea by channels where 10 or 20 lines of in-stream turbines would be placed. The
area of the basin could be several hundred km2 or possibly thousands of km2, with
about one channel per 100 km2. Smaller basins could be used with one channel.
Most future sites would be along the shore. A typical basin could then form a
semi-circle along the shore but more favourable sites could be available such as
narrow small or large gulfs.
The concept of a channel (TG) linking the basin to the sea is shown in Fig. 5.
The length would be based on the mean tidal range as well as on turbines
data. The width could be around 500 m for very large basins, or 100 to 200 m for
small ones. The depth could be 15 to 20 m below the low sea level; this may
require some dredging or filling. To allow for a significant water speed, the bottom
should be lined, for instance by 0,50 m of concrete placed in calm water. In
stream turbines may have an horizontal or vertical axis. Various lay out of turbines
in the channels may be used.
The channel sides would be formed by dykes 25 m high, supporting a low
head and greatly reduced wave impact. They could be as shown in Fig. 6 (a).
The channel would be separated from the sea by gates, to be opened for
473
Q. 96 – R. 35
about 4 hours within a six-hour half
be quite low, but the wave impact
spillway gates could be used, but
specific also for the construction
possible.
tide. The differential head on the gates would
might be high. Solutions similar to those for
the specific conditions may favour solutions
method. Innovative designs would also be
For the main closure dyke, recent progress in breakwater design and
dredging efficiency favours a solution as shown in Fig. 6(b), which would be
suitable for an optimal construction program of largest schemes limited to 6 or 7
years all included. For smaller sites and length of dykes under 5 or 10 km, using
rockfill dykes may be less expensive according to quarries availability.
Fig. 6(a)
Channel dike
Digue du chenal
Fig. 6(b)
Dam breakwater
Digue brise-lame
474
Q. 96 – R. 35
2.3.
COST
A first comparison is made with traditional tidal plants designs, i.e. bulb units
operating one way under a 4 or 5 m head.
The cost per MWh of such tidal plants includes two parts:
- The main dyke and sluices (gates) allowing the basin filling. For a same
basin using Tidal Gardens, the main dyke and the Sluices are about the
same but the yearly energy is about one third higher and the cost per MWh
thus 25% lower.
- The largest part for the plants and especially for their civil engineering. The
cost per MW of electromechanical part may be similar for Tidal Gardens but
the civil engineering cost per MW of channels is much lower than for tidal
plants; the overall cost per MW is thus significantly lower and the yearly
supply is 3500 or 4000 hours of the rated power instead of 2000 hours. The
cost per MWh is thus reduced by about 60%.
- And the total cost per MWh is close to half of tidal plants cost for best tidal
sites and less than half for a tidal range of 4 or 5 m. It may be in the range of
50 €/MWh for turbines and channels and 10 to 50 € / MWh for the main
dyke.
- The cost per MWh of Tidal Gardens is also lower than In Stream Turbines in
natural conditions. The water speed is higher, always the same, in the same
direction. Turbines may be placed and maintained in calm water easily,
anchored and linked electrically at low cost and used more hours per year.
Conditions of operation and maintenance are much different. There are few
places where the cost in natural conditions may be under 150 €/MWh when
the cost of Tidal Gardens will be usually under 100 €/MWh.
- The cost per MWh of the main dyke and ancillary works varies significantly
with each site. It may be as low as about 20 € / MWh for favourable shore
shapes such as narrows gulfs but also for very large schemes where the
length of dykes per yearly TWh is few Km or where the local conditions (sea
depth and available quarries) favour low cost dykes.
Ancillary works may include shipping facilities; their cost per MWh will be
usually much less than the cost of main dykes.
A part of the dykes cost may also be paid by the relevant facilities such as
shore protection and possibilities of low cost energy storage or wind farms and
industrial or touristic developments. For many world sites the cost per MWh of the
main dykes and ancillary works may thus be well under 50 € / MWh and the total
cost of power under 100 € / MWh.
Such costs will increase slightly for tidal ranges as low as 3 or 4 m and
significantly under 3 m.
475
Q. 96 – R. 35
3.
EVALUATION OF YEARLY ENERGY
To illustrate the potential yearly energy estimation as indicated in point 2.2
we develop in this paragraph an application to the French Channel coast.
3.1.
TIDES CHARACTERISTICS
The reference site is Saint-Malo where we had the opportunity to treat the
1981 - 2007 period for tidal energy estimation purpose (amplitude and timing of
the corresponding 19,053 tides).
The average tide amplitude at Saint-Malo on this period is 7.86 m. A
correlation between tides amplitude and timing is obvious for this given site.
Other correlations are underlined in the following figure where comparisons
are made with Saint-Malo, for the other 4 harbours, considering tides amplitudes,
and time of maximum sea levels.
These comparisons are based on 5 neap tides (P1 to P5), 12 mean tides
(M1 to M12) and 5 spring tides (G1 to G5).
Fig. 7
Tides amplitudes of the other Channel 4 harbours compared
to those at Saint-Malo
Amplitudes des marées entre 4 ports de la Manche comparées à celles
de Saint- Malo
476
Q. 96 – R. 35
In summary:



At Roscoff the tide amplitude is roughly ever about 70 % of Saint-Malo’s
one, leading to an estimated average tide amplitude of 5.50 m.
At Cherbourg the tide amplitude is roughly ever only about 50 % of SaintMalo’s one, leading to an estimated average tide amplitude of 3.93 m.
At Dieppe as at Boulogne-Sur-Mer, the ratio varies with the amplitude,
and represents respectively +12% and +7% for neap tides, 85% and 80%
for mean tides, 75 and 70% for spring tides, that means roughly in
average an amplitude of 6.70 m at Dieppe and 6.33 m at Boulogne-SurMer.
The differences in time table are in average:


Advance of 62 minutes at Roscoff (about one hour)
Delay of 113 minutes at Cherbourg, 284 minutes at Dieppe and
300 minutes (5 hours) at Boulogne-Sur-Mer.
Combining operation of various basins located close to these various
harbours could allow a quite continuous production.
3.2.
POSSIBLE YEARLY ENERGY PRODUCTION
For a basin area S in km², a two ways operation of this basin, a ratio of
installed capacity in MW/km² of 0.2 hm², the possible yearly energy production in
GWh/km² is summarized in table 8.
Table 8
Possible yearly energy production
Production possible annuelle d’énergie
Site location
Saint Malo
Roscoff
Cherbourg
Dieppe
Boulogne-Sur-Mer
Installed capacity (MW/km²)
12.5
6
3
9
8
Yearly energy (GWh/km²)
43
21
10.5
31
28
477
Q. 96 – R. 35
4.
ENVIRONMENTAL AND ECONOMICAL IMPACTS
Environmental and economical impacts of large scale projects such as
Tidal Garden should be thoroughly studied, without any bias, and with modern
methods.
Experience from previous off and near-shore projects (offshore wind farms,
in-stream turbines, tidal plants) can be a valuable base for these studies, but
attention must be paid that Tidal Garden is a specific concept with its own
features and must be so considered. Main topics identified today are described
hereunder.
4.1.
TIDES
Tidal range is a main parameter to assess environmental impacts as it
affects marine environment through temperature, salinity, currents, light,… Tidal
range in the basin should then remain as close as possible from the natural tidal
range.
Preliminary calculation (analytic and model) showed about 2 hours time
shifting, 20-30 % range attenuation at spring tide and 0-10 % attenuation at neap
tides.
4.2.
MARINE ENVIRONMENT
Main marine environment component are salinity, sedimentation, tide
range, currents and turbulence. Those should be the less possible affected by
the project.
Impact analysis is first carried out at global basin scale, rather than at local
scale at the entry/exit points or close to the dykes.
 Longshore drift will be modified as shores will be protected against swell,
 Currents are modified as well but impact should be moderated except at
entry and exit points.
calculations show that water remains in the basin
approximatively as long as without tidal garden. Temperature should then
barely be impacted.
 Preliminary
These preliminary considerations should be taken with care and confirmed
with hydro-sedimentary model. It should be noted that hydro-sedimentary
working of marine environment is a complex phenomenon, affected by several
478
Q. 96 – R. 35
human and non human parameters, that does not always lead to equilibrium or
acceptable situation for the populations.
4.3.
BIODIVERSITY
Main threats on biodiversity are listed hereunder with impacts during
construction at first and during exploitation after, with some preliminary
comments. Opportunities created by tidal gardens are detailed later.

Impacts during operation
Dyke physical presence




Channels and turbines


Cables
Vibration and noise



Pollutions
(painting,
chemical products)
Electromagnetic fields




Marine habitat destruction – 3 to 5 km²/TWh/year to be
compared
to
few
for
offshore
wind
farms,
10 km²/TWh/year
for
photovoltaic
energy
or
100 km²/TWh/year for onshore HPP
Recolonisation possible
Impassable for marine fauna
Special attention to dyke localisation with respect to
sensitive areas
Relatively high velocities – risk depending on the specie
Collision risk depending on turbine structure, depth and
location, specie’s dimension, displacement ability;
collision risk to be mitigated by appropriate design.
No cable laying in the seabed (cables along the dykes)
Similar to usual in-stream turbines (those being however
located in naturally high and noisy currents area);
Limited knowledge on this topic available, to be built up
for both T.G and in-stream turbines
Similar risk as for other marine works
Regulated by law, risk mitigated by know-how
Lower than for other marine energies (see cables, above)
Limited knowledge on this topic available
Note: At the basin’s scale, tidal gardens are quite permeable for biodiversity. This should
be confirmed by in-depth studies and experimentation, but one should remember that
French tidal plant in “La Rance” estuary, which has no direct connection between the sea
and the estuary (unlike tidal gardens) is reputed permeable to life, for planktonic
organisms and bigger animals.1. Study of migration schemes, rest, feeding and
reproduction areas is mandatory to correctly assess project’s impacts and take them into
account in the layout.
Le Mao P., 1985, Peuplements piscicole et teuthologique du bassin maritime de la
Rance, impact de l’aménagement marémoteur, EN-SAR, 125 p
1
479
Q. 96 – R. 35
Impacts during construction

Impacts during construction should be similar to those caused by largescale marine works. Noise and vibration, sediment suspension, pollution,
(permanent or not) habitat destruction, may be generated by dredging and
reclamation operations, concreting, equipment placing.
Impact assessment should follow well established methods, typically used
for large scale dredging operation, port or offshore wind farms construction.
Those works are regularly carried out and techniques exist in order to mitigate
impacts.
Pile driving or drilling
Sea bed changes
(Dredging/reclamation)
Ships
and
heavy
equipment presence
4.4.





Pile driving should be avoided or very reduced.
Risk of resuspension of sediments and induced turbidity
increase;
Commonly monitored and mitigated in marine works
Similair to other marine works
Methods to be adjusted to local environment
OTHER IMPACTS
Some other impacts are listed below.
Landscape



Navigation and
communication routes



Safety


4.5.
Dykes and gates only are visible, 10 to 15 m above low tide
Near shore dyke stretches to be compared to large bridges
that are usually higher
Offshore stretches to be compared to visual impact of 150
m high windmills
To be avoided as much as possible during site selection
Technically possible to maintain communication cables
Options to be further studied for navigation (open and
turbine free channel, sluice,…)
No risk of dam break induced flood (compared to HPP)
Safety measures to be taken, restricted access area to be
delimited, as for any energy production site
SOCIO-ÉCONOMIC ENVIRONMENT
Main socio-economic impacts of such a project are similar to those of an
offshore wind farm project: no population displacement, increased economic
480
Q. 96 – R. 35
activity thanks to large scale works (civil, mechanical, electrical works; economic
activity for maintenance and operation).
Numerous jobs can also be created thanks to additional purposes that can
be conferred to the tidal garden project, as listed below.
Important also is the current uses of the tidal garden area, especially the
tidal garden basin. Use can be fishing, shellfish farming, aggregate pit
operations,… The analysis should be carried out carefully, case by case
depending on each site.
4.6.
FUTURE PROSPECTS
This preliminary impact review does not claim to be exhaustive, but lists
main expected impacts of tidal gardens.
From this review following conclusions can be drawn:
 Many topics have been studied, more or less extensively and many


uncertainties are not specifically linked to tidal gardens, but more
generally to marine renewable energies, that should include in the future
the tidal gardens;
Impacts should be compared to other large scale marine works on one
hand, and to other renewable energies (marine or not) on the other hand.
Hydrodynamic and hydrosedimentary modelling is mandatory to assess
impacts on the environment;
Environmental impact assessment should then be carried out carefully,
respecting national and international state of the art methodologies, without bias.
As such, French experience in the La Rance estuary, widely studied and
documented should not be transposed to tidal gardens. The estuary environment
is particularly sensitive, and stands for about 1 % only of the French power
potential.
Finally, environmental compensatory measures should be sought out even
if those are barely implemented in renewable marine energy project today, but
this topic is being currently studied2.
2 UICN France (2014) : Développement des énergies marines renouvelables et
préservation de la biodiversité. Synthèse à l’usage des décideurs. Paris, France
481
Q. 96 – R. 35
5.
UTILIZATION BEYOND ENERGY SUPPLY
A tidal garden project should be set up as main component of town and
country planning. Use of resources should be efficient and utilization beyond
energy supply by turbines can play a major role in the decision process.
Some opportunities for utilization beyond energy supply of a tidal garden
project are described below.
5.1.
MARINE ENVIRONMENT PROMOTION
Environment modification due to dyke and channel construction is a threat
for biodiversity but could be also an opportunity if designed in sensible way,
amongst others thanks to the reef effect.
New marine structures are new areas that will be colonized by several
organisms, depending on depth, and particularly in structures haven been
designed taking this aim into account.
Areas near the dykes will be refuge areas, as navigation and fishing will be
prohibited.
Those opportunities should be carefully studied in order to analyze the
biodiversity change in terms of biomass and variety of species. Special attention
should be paid to non native and invasive species.
These opportunities could be considered as a compensatory measure to
the project in order to mitigate the impacts, keeping in mind that it is not possible
to compensate a habitat loss by another habitat.
Those considerations are applicable to any marine renewable energy
project. Knowledge today is limited, and common efforts should be made to
enhance the know-how.
In a more prospective way, adequate gate operation could contribute to
limit saltwater to rise back in estuaries subject to salinization.
482
Q. 96 – R. 35
5.2.
SHORE PROTECTION
 Marine submersion
Several shorelines are affected by swells from open sea and from wind.
With a representative wave period from Vendée and Charente-Maritime (France)
shoreline (4 to 6 seconds), dykes from tidal gardens have a very significant effect
on the transmitted wave height and therefore contribute to protection against
marine submersions.
 Shoreline erosion
There is a direct link between transmitted swell and shoreline erosion.
Shoreline drift is responsible for sandy material loss at several beaches along the
shore. Decrease in swell intensity will decrease this drift. It can then protect the
shoreline against erosion but can lead to threats to biodiversity. A hydrosedimentary model coupled with a thermic model is mandatory to assess the
impact on this complex phenomenon that may not be naturally acceptable to
populations. Local effect at entry and exit points makes no doubt; local
bathymetry will be affected.
5.3.
ADDITIONAL ENERGY PRODUCTION AND STORAGE
A tidal garden development project can create opportunities to set up wind
farms within the basin at controlled costs.
Cable laying costs and offshore construction costs increase the budget of
offshore wind farms. Those extra costs are mostly saved in a tidal garden project:
cable costs can be shared with the existing tidal garden projects, and swell in the
basin is significantly reduced, which makes design, work and operation condition
much better.
As a calculation basis, wind farms could be set up on half the basin. With
about 10 MW/km² installed operating about 2500 hours per year, that gives about
12.5 GWh/km². This increase of the project power production could be done at
competitive cost, and could be coupled to an energy storage device, as
described below. It can be particularly interesting at site with moderated tide
range.
However, wind farms could seriously increase environmental impact of the
project.
Energy produced by a tidal garden is very predictable at long term, but
irregular over half a tide and over 14 days. Demand is also irregular over
483
Q. 96 – R. 35
24 hours and over longer time period, with a more or less predictive global
evolution.
It is relevant to plan a storage device for the energy produced by the tidal
garden, by means of pumped-storage hydroelectricity. Different designs should
be studied, but all of them take advantage of reduced swell in the basin: PSH
with one reservoir, the other being the sea; PSH with two reservoirs in the basin;
conventional marine PSH, upper reservoir being located onshore.
5.4.
INDUSTRIAL AND NON INDUSTRIAL ACTIVITY
Different types of industrial and non industrial activities could take
advantage of a tidal garden project. Some of them are listed below, along the
dykes or within the basin. This list is obviously non exhaustive and should be
adjusted and completed site by site.
In the basin


Along the dykes (basin
side)


5.5.
Favorable conditions to large scale aquaculture or shellfish
farms, thanks to calm and constantly renewed water
Construction materials extraction at main sedimentation
areas created by change in hydrosedimentary working
Fishing ports and marinas in calm water; sandy beaches or
artificial islands for nautical and tourist activities
Deep see ports sheltered by the dykes, land reclamation for
chemical plants, refineries, LNG terminals,…
FUTURE PROSPECTS
Utilization beyond turbines energy production can be critical in the decision
process for a tidal garden as it allows significant increase of the benefits and
sharing of the costs. This can be compared to large multi-purpose hydropower
dams.
Wind farms and PSH make also possible to optimize global energy
production for the project.
Finally, additional usages of a tidal garden project shows low environmental
impacts increase compared to benefits.
This shows that a tidal garden project should be considered as a global
land planning project, able to economically stimulate a large area, beyond pure
energy production.
484
Q. 96 – R. 35
6.
THE WORLD POTENTIAL
The technically feasible potential is linked with the natural tidal range hm
and with the water area where depth is acceptable for dykes construction. A very
rough evaluation could be made where hm is over 3 m and a water depth below
low tides level less than about 20 m. Such world area of 400 000 km2 (20 000 km
x 20 km) with an average tidal range of 4 m would allow technically an energy
supply of (0,7 x (4)2 x 400 000), i.e. about 5 000 TWh/year.
1 000
The economically feasible potential is based upon the cost comparison with
other acceptable energy sources available mid century. The range of acceptable
cost including transport may be close to 100 €/MWh but varies with countries.
Some very rough evaluations of potential are given below for 20 countries. For
most of them, the possibilities are totally linked with the advantages of the Tidal
Gardens new solution. Many choices may also be favoured by the extra facilities
from calm water basins: shore protection against waves or abnormal water levels,
energy storage, low cost large wind farms, industrial or touristic development
which may pay some part of the dykes.
The costs of energy transport may be a key element for comparison
because a significant part of low cost tidal energy is one or few thousands Km far
from customers (a transport cost of 10 €/MWh for 1 000 Km may be possible for
very large capacities).
Storage is also a key problem for most renewable energies. Relevant
facilities from tidal basins may be very useful for all energy sources. The need of
storage for tidal energy may be reduced if the tides timetable is not the same for
various tidal sites of a country.
Ten Countries have a very large cost effective potential: Russia, Canada,
Australia and China may have each about 200 TWh/year, France, U.K., India,
Brazil, South Korea, Argentina about 100 TWh/year.
Russia has the largest world potential, essentially in 3 places.
-
-
-
The Western site which may include the Mezen Site already studied in detail
and probably the very large site of Chechskaya (8 000 km2) of lower tidal
range and perhaps the White Sea (Fig. 9). The total supply may be well over
100 TWh/year, 1000 km from Moscow and St Petersburg.
The Tugurskaya site in Southern Okhotsk Sea may probably be extended
as per Fig. 10 to a much wider area of lower tidal range; 100 TWh/year
could be used in Siberia, China (Harbin) or Japan.
The Penzhinskaya site in Northern Okhotzh Sea has a potential of
200 TWh/year but the extremely cold conditions and the distance from
Customers may prevent or at least delay its utilization.
485
Q. 96 – R. 35
Fig. 9
Chechskaya site / Site de Chechskaya
Fig. 10
Tugurskaya site / Site de Tugurskaya
Canada has two sites with high tides:
 The well known Fundy Site where favourable sea depth favours short
dykes and very low cost (Fig. 11) for about 40 TWh/year rather close to
Montreal and New York.
 The Ungava Bay may supply 100 TWh/year but the cost delivered to
Montreal or New York may be over 100 €/MWh.
Possibilities on Pacific Ocean seem much lower.
486
Q. 96 – R. 35
Australia has an excellent potential on Northern Coast West of Darwin with
a tidal range of 7 m and a possible supply up to 200 TWh/year. It is very far from
most Australia needs and closer to Java. The tidal Gardens Solution favours the
Eastern Site North of Brisbane (Fig. 12) where tidal range is under 5 m but the
sea depth conditions favourable: 50 TWh/year may be supplied at low cost
1500 km from Sydney. Some TWH/year may also be supplied very close to
Melbourne.
Fig. 11
Fundy site / Site de Fundy
Fig. 12
Eastern site North of Brisbane / Site du Nord-Est de Brisbane
China has a huge potential along over 3000 km and the sea depth favours
the construction of dykes 20 km from shore. But the tidal range is as average
487
Q. 96 – R. 35
about 3 m and could hardly be used with past solutions. The Tidal Gardens are
cost effective in Chinese conditions and could supply 100 or 200 TWh/year very
close to energy needs. The additional facilities of energy storage, low cost wind
farms, shore protection, industrial or touristic development could be extremely
important, at least from Guangdong to Qingdao.
Brazil has about same conditions as China: long coasts, reduced sea depth
and rather low tidal range. The possibilities seem essentially along 1000 km in the
Northern Coast west of San Luis where tidal range is about 3 m. Supplying 50 to
100 TWh/year seems a reasonable target. Management of the Amazon Delta may
not be an utopia.
France has much potential close to needs and the experience of La Rance
since 50 years. The potential is close to 100 TWh/year where tidal range is over
6 m; it is close to 150 TWh/year with the Tidal Gardens Solution which may apply
not only in the Channel but also in the West Coast. 3 of 8 possible large sites are
presented in Fig.13 and may supply 80 TWh/year with 200 km dykes at an
attractive cost.
U.K. The Tidal Gardens solution may increase dramatically the cost
effective potential; the Severn site may be possibly much enlarged (Fig.14)
accepting a slightly reduced tidal range and large sites North of Liverpool may
also supply over 35 TWh/year. There is also a significant potential in the Eastern
Coast. The total tidal potential may be close to 80 TWh/year. A small part of the
basins may be devoted to Energy Storage used also for wind energy.
Fig. 13
3 possible large sites in France
3 grands sites possibles en France
488
Q. 96 – R. 35
Fig.14
Severn example
Exemple de la Severn
South Korea has few sites with a tidal range of 6 m but very large areas with
4 or 5 m. The cost effective potential if using Tidal Gardens may reach
100 TWh/year; it may be an excellent opportunity for the overall economy of the
country.
United States have high tidal range in large areas in Alaska but the sea
depth is too important in quite all sites. However an excellent site is close to
Anchorage and may supply up to 50 TWh/year at low cost. It is much more than
local needs but the cost delivered to Seattle by sea electric line may be
acceptable mid century.
Argentina has 3 sites:
-
The San Antonio Gulf is limited to few TWh/year by the sea depth.
The two Gulfs of Puerto Nuevo with 4000 km2 and about 4 m tidal range
may supply over 30 TWh/year at low cost (Fig. 15).
The Patagonia may supply some 50 TWh/year associated with the huge
offshore or onshore wind potential there. The cost delivered to Buenos Aires
or Sao Paulo may be acceptable.
489
Q. 96 – R. 35
Fig.15
Golfo Nuevo site
Site de Golfo Nuevo
-
-
India has essentially three sites.
The two Western sites of Kutch and Bhavnagar Gulfs which total 4000 km2
with a tidal range of about 5 m and may supply at a rather low cost
50 TWh/year and be associated to solar energy with a common energy
storage.
There is also a possibility in the Bengal Gulf with low tidal range but very
large areas.
There are also ten countries which may supply each between 10 and
50 TWh/year if using the Tidal Gardens solution.
In America: Panama and Chili.
In Africa: Mozambic (Beira)
In Europe: Netherlands and Germany
In Asia: Pakistan, Bangladesh, Vietnam, Myanmar, North Korea.
The realistic world tidal potential seems thus in the range of 1500 TWh/year
with 100 000 km2 of basins. Adding low cost wind Mills on one third could add
1000 TWh/year (30 GWh/year per km2). Present hydropower supplies
3500 TWh/year with 350 000 km2 of reservoirs. Nuclear Power supplies
3000 TWh/year.
The impact on shore protection may be very important for countries with
large deltas such as Vietnam or Bangladesh.
Some countries which have favourable or acceptable tides have little
potential because the sea is too deep close to shore: it is the case of most Africa,
Portugal, Ireland, Colombia, most Alaska.
490
Q. 96 – R. 35
7.
POSSIBLE SCHEDULE OF TIDAL ENERGY UTILIZATION
Most of the potential is for large schemes of some GW and up to 10 GW
and relevant investments for one site are similar to investments for very large
hydropower schemes or for nuclear plants. It is thus likely that these sites will not
be developed before 2025, i.e. before the experience and optimization from
smaller schemes. But there are worldwide hundreds sites for some hundreds MW
where the cost per MW may be slightly higher than for the best huge sites but
however acceptable. It will be the opportunity for optimizing designs and
equipments for the main development.
Ten countries have the technical capacity and the potential justifying an
early implementation of such preliminary schemes. It will be also the best way of
checking the impacts of the solution and of improving them.
The tidal world yearly investments will probably not be very high before
2025. But it could be 50 Billions / year after 2030 because it will include the
investment for power supply and also for facilities such as energy storage, wind
farms, industrial developments.
8.
ENERGY STORAGE AT SEA BEYOND TIDAL AREAS
A small part of tidal basins may be used for energy storage by basins of
which the dykes are built in calm water. But where there is no tidal basin, there
are many other possibilities of storing energy along shore or offshore i.e. of using
the sea as one basin of a Pumping Storage Plant (PSP).
-
-
-
An upper basin may be placed on a cliff and the sea used as low basin.
A basin may be created along shore and used as high basin: there are
many alternatives for choosing the operating head and relevant dykes
height. This head may well be as low as 10 or 20 m or over 50 m.
A basin may be fully offshore and used as low basin or high basin.
The cost of Energy storage fully at sea is generally acceptable only for
rather large schemes over 500 MW except in Islands where much smaller
schemes may be cost effective.
A great advantage as compared with traditional PSP in mountains is the
much better possibility of modifying the operation in very short time because
the two basins are very close and are not linked by tunnels. Some hundreds
GW of PSP at sea may be built before 2050.
491
Q. 96 – R. 35
9.
SHORE PROTECTION BEYOND TIDAL SCHEMES
Beyond areas of possible tidal schemes the need of shore protection will
also increase along the century for three reasons:
-
The human risk from tsunamis or typhoons.
The much increasing cost of buildings and infrastructures.
The increase of oceans level and relevant disastrous impacts on some
places such as deltas.
Where protections are not possible onshore the cost of offshore dykes may
be acceptable, between 10 et 50 millions €/km. They could withstand some hours
the impact of tsunamis or typhoons with a 10 m head, and/or withstand full time
heads of few m:
-
Adding to dykes some sluices and/or pumping stations will favour the
choice full time of the optimum water level along shore.
CONCLUSION
Technical solutions studied up to now are poorly adapted to the very specific
data of tidal energy and thus too costly. A new solution, the “Tidal Gardens” may
be cost effective for 1 500 TWh/year in 20 countries even with natural tidal ranges
as low as 3 or 4 m.
The environmental impacts seem better than for other renewable energies.
The large relevant basins may be used also for very large low cost wind farms,
industrial and touristic developments. Energy storage by PSP at sea and shore
protection are favoured by such tidal plants but may also be obtained without
Energy supply where tidal range is very low.
After 2030 the yearly investment for various dams at sea could be higher
than the past or future yearly investment for traditional dams.
SUMMARY
The Energy potential of Rivers and of Tides is about the same. Hydropower
supplies 3500 TWh/year and Tidal Energy 1 TWh/year.
492
Q. 96 – R. 35
The reason of this surprising gap is not the environmental impact which
may be actually more favourable for tidal energy (Shiwah Plant in Korea was
made for improving impacts).
The true reason is that the traditional plants design successful in
Hydropower and studied since 60 years for tidal energy is poorly adapted to the
specific requirements of cost effective tidal energy, i.e. a very low operating head
of about 2 m and flows of dozens or hundreds thousands m3/s.
A more recent solution is based on In Stream Turbines (similar to Wind
Mills) which may be cost effective with prevailing water speed over 3 m/s: a row
of such turbines may use a water head to 0,20 m but there are few natural world
sites with favourable data of water speed and local conditions (waves, access,
links to grid, ….) and the cost effective potential is very low.
A new solution (Tidal Gardens) uses large basins along shore linked to sea
by wide channels in which are placed 10 or 20 rows of In Stream Turbines; they
are built and operated in optimal conditions of water speed, construction,
maintenance and link to grid. They may use a large part of available energy and
operate both ways, i.e. most time. The optimal water speed i.e. full capacity may
be kept through adjusting time of channels opening and of number of operating
turbines. This solution has three key advantages as compared with traditional
plants:
- The cost par MW is lower and the yearly energy supply is 4000 hours of the
capacity instead of 2000, thus halfing the cost per MWh.
- This attractive cost applies also for natural tides of 3 to 5 m, the number
and investment of turbines being proportional to the tidal range. The tidal
energy is thus not limited to exceptional sites and may be used in twenty
countries instead of 5 or 10.
- The possibility of using a two ways operation keeps in the basin and along
shore the tidal conditions close to the natural ones (shifted by 2 hours) and
huge waves or detrimental very high water levels are avoided.
Negative and positive environmental impacts deserve careful studies and
comparisons, for a same energy, with other energy sources. They seem better for
these tidal schemes than impacts from traditional Hydropower. Large basins of
calm water along shore favour many opportunities: basins for energy storage
built in calm water and using few per cent of the main basin area, low cost wind
farms producing as much as tidal energy per km2, fish farming, touristic
development along shore, industrial and harbour development along the main
dyke of the basin 20 km from shore. Shore protection against waves and possible
control of the highest water levels may be extremely useful in many countries and
mitigate the impact of oceans level increase.
The world cost effective tidal energy supply may be 1500 TWh/year half of
the present Hydropower or nuclear energy. It is linked with natural tidal range
493
Q. 96 – R. 35
over 3 m and moderate sea depth (dykes less than 30 m high). Huge wind
energy in tidal basins shall be added possibly for 500 or 1000 TWh/year. About
ten countries could supply each 50 to 200 TWh/year: Russia, China, Canada,
Australia, France, U.K, India, Brazil, Argentina. Other countries could each
supply 10 to 50 TWh/year: U.S.A. (Alaska), Netherlands, Germany, Panama,
Vietnam, Pakistan, Mozambic, Myanmar, North Korea.
Most potential is by 100 very large sites between 1 and 10 GW to be
implemented after 2025.
But there are hundreds of sites of hundreds of MW: 10 or 20 could be
implemented before 2025 for optimizing the technical solutions and precising the
impacts. Larger sites, using similar solutions, will thus be developed very safely.
RÉSUMÉ
L’énergie potentielle des rivières et des marées est du même ordre.
L’hydroélectricité traditionnelle produit 3500 TWh/an, l’énergie des marées
1 TWh/an.
La raison de cet écart surprenant n’est pas l’impact sur l’environnement qui
peut en fait être meilleur pour l’énergie des marées. La vraie raison est que les
usines traditionnelles de l’hydroélectricité étudiées depuis soixante ans pour les
marées sont mal adaptées aux conditions souhaitables correspondantes, c’est-àdire à une très faible charge, de l’ordre de 2 m et à de très forts débits, de
dizaines ou centaines de milliers de m3/s.
Une solution plus récente est basée sur les hydroliennes, analogues aux
éoliennes : elles peuvent être efficaces et utiliser une charge de 0,20 m avec une
vitesse continue de plus de 3 m/s ; mais il y a peu de sites mondiaux avec cette
vitesse et leurs conditions physiques locales sont coûteuses. Le potentiel
mondial à un cout acceptable est faible.
Une nouvelle solution (Les maréliennes) utilise de grands bassins le long
de la côte fermés par une digue. Ils sont reliés à la mer par des chenaux dans
lesquels sont placés 10 à 20 rangées d’hydroliennes : elles sont construites,
exploitées et raccordées dans les meilleures conditions : elles fonctionnent dans
les deux sens c’est-à-dire la majorité du temps : la vitesse de l’eau optimale
(c’est-à-dire la pleine puissance) peut être maintenue en agissant sur la durée
d’ouverture des chenaux et le nombre d’hydroliennes en service.
Cette solution a trois avantages essentiels par rapport aux usines
traditionnelles :
494
Q. 96 – R. 35
-
-
Le coût par MW est plus faible et l’énergie annuelle est 4000 heures de la
capacité au lieu de 2000 d’où un coût au MWh réduit de moitié.
Le coût attractif s’applique aussi aux zones de marées de 3 à 5 m, le
nombre et l’investissement des hydroliennes étant proportionnel à la
hauteur de marée. Le potentiel n’est donc pas limité à quelques sites
exceptionnels mais s’étend à 20 pays.
La possibilité d’opérer économiquement dans les 2 sens garde dans le
bassin et à la côte les conditions naturelles de marée (décalées de
2 heures) en évitant les fortes vagues et les hautes mers exceptionnelles.
Les impacts environnementaux positifs et négatifs doivent être étudiés très
soigneusement et comparés, à énergie égale, aux autres sources d’énergie.
L’impact parait meilleur que celui de l’hydroélectricité traditionnelle. Les grands
bassins d’eau calme favorisent des services importants complémentaires :
bassins de stockage d’énergie construites en eau calme et utilisant quelques
pour cent de la surface du bassin, fermes éoliennes économiques pouvant
doubler l’énergie par km2, aquaculture, tourisme à la côte, industries et ports le
long de la digue à 20 km en mer. La protection du rivage contre des crues de très
hautes eaux, payée par l’électricité, peut être essentielle dans beaucoup de
pays.
Le potentiel peut être estimé pour les zones où la marée moyenne est de
plus de 3 m et la hauteur de digues inférieure à 30 m.
Le potentiel mondial réaliste est d’environ 1500 TWh/an. On peut y ajouter
500 ou 1000 TWh/an d’énergie éolienne économique dans les bassins (l’énergie
nucléaire mondiale est 3000 TWh/an).
Une dizaine de pays ont chacun un potentiel de 50 à 200 TWh/an : Russie,
Chine, Canada, Australie, France, U.K., Inde, Brésil, Argentine. D’autres peuvent
produire 10 à 50 TWh/an : U.S.A. (Alaska), Pays Bas, Allemagne, Panama,
Vietnam, Pakistan, Myanmar, Corée du Nord.
La majeure partie du potentiel mondial correspond à 100 grands sites de
1 à 10 GW, entrepris probablement après 2025. Mais il y a des centaines de
sites de quelques centaines de MW. Dix ou vingt peuvent être en service dans
10 ans, permettant d’optimiser les techniques des plus grands sites et de
préciser les impacts.
495
Q. 96 – R. 14
COMMISSION INTERNATIONALE
DES GRANDS BARRAGES
------VINGT-CINQUIÈME CONGRÈS
DES GRANDS BARRAGES
Stavanger, Juin 2015
-------
PUMPED STORAGE PROJECTS BETWEEN EXISTING RESERVOIRS IN
SPAIN BY GAS NATURAL FENOSA (*)
Javier BAZTAN
Hydraulic Director; Gas Natural Fenosa IDG
Nuria RODRIGUEZ
Hydraulic Project Manager; Gas Natural Fenosa IDG
Ana MARTÍN
Hydraulic Project Engineer; Gas Natural Fenosa IDG
SPAIN
1.
INTRODUCTION
Spain is facing many challenges trying to integrate a large amount of
renewable energy (wind and solar) into real-time dispatch of its power generation
to meet electricity demand.
To meet sustainable criteria for grid stability and reliability, Gas Natural
Fenosa (GNF) is looking into alternative storage projects and especially Pumped
Storage Projects (PSPs) using existing reservoirs. GNF is developing several
PSPs, currently at different stages, from preliminary studies to bidding process
for starting construction. These projects will allow to store energy produced from
other resources, such as wind, at times when it is difficult to utilize it on the power
grid or integrate it into the power system, and afterwards release the energy at a
time when it is needed
PSPs need two reservoirs for their operation, as lower and upper
reservoirs. Three of the new PSPs in North- Western Spain under study by GNF
are: Belesar III PSP: with an installed capacity of 210 MW, uses the head
between Belesar and los Peares reservoirs. Salas – Conchas PSP: with an
(*)
Station de transfert d´énergie par pompage entre les réservoirs existants dans le centre
de l’Espagne de Gas Natural Fenosa.
174
Q. 96 – R. 14
installed capacity of 375 MW, uses the head between Salas and Las Conchas
reservoirs. Edrada PSP: with an installed capacity of 767 MW, uses the head
between Edrada and San Esteban reservoirs
This paper will focus on the role of existing dams and reservoirs in the
design of new PSPs, and particularly in these three projects currently under
study, explaining the advantages, requirements and limitations introduced in the
projects by the presence of these already built infrastructures.
The main objectives of this paper are to present the unique design
challenges of these three pumped storage projects related to their dams and
reservoirs, and to describe the specific considerations taken into account in the
design and planification of the construction work of them. These include the study
of: distance between reservoirs/ waterways length ratio, study of the head
between reservoirs and its variation, pump-turbine and motor-generator unit
selection, intake construction in flooded areas and necessity to lower the
reservoir level, minimization on affection on existing reservoirs operation by both
construction works and future PSP operation, environmental and other
constraints associated with the development of a PSP.
2.
2.1.
PROJECTS PRESENTATION
BELESAR III PSP
Belesar and Los Peares dams are located on the Miño River, near the city
of Lugo in North -Western Spain. Both dams are owned by GNF, and entered in
service in 1963 and 1955, respectively.
Belesar reservoir is 47 km long and it contains an operating volume of
654 million m3. Belesar dam is an arch type dam 132 m high above foundation. It
was the highest dam at its time in Spain. On the other hand, Peares reservoir is
22,5 km long and contains an operating volume of 182 million m3. Peares dam is
a concrete gravity type dam with a height of 118 m above foundation.
175
Q. 96 – R. 14
Fig. 1
Belesar and Los Peares dams
Barrages de Belesar et de Los Peares
Maximum turbined flow will be 180 m3/s, while 169 m3/s in pumping mode.
The power plant will be equipped with 2 reversible Francis units (2 x 105 MW).
The main features of the waterways are the following: upper intake/outlet
structure, upper level headrace tunnel, pressure shaft, lower level pressure
tunnel and penstocks, draft tube tunnels, surge tunnel, a tailrace tunnel, and a
lower intake/outlet structure. The powerhouse complex and waterways will all be
underground. The distance between reservoirs is approximately 3 km for a gross
head of 137 m.
Fig. 2
Belesar III PSP Project 3D
Centrale de pompage-turbinage de Belesar III 3D
176
Q. 96 – R. 14
2.2.
SALAS-CONCHAS PSP
Salas and Las Conchas dams, owned by GNF, are located on the Salas
and Limia Rivers, in North -Western Spain near the North frontier with Portugal.
Both dams entered in service in 1971 and 1949, respectively.
Salas reservoir contains an operating volume of 75,6 million m3. Salas dam
is an buttressed dam in its central part, with two long gravity dams locking both
abutments, 50 m high above foundation. On the other hand, Las Conchas
reservoir contains an operating volume of 69 million m3. Las Conchas dam is a
concrete gravity type dam with a height of 46 m above foundation.
Fig. 3
Salas and Las Conchas dams
Barrages de Salas et Las Conchas
The maximum flow in turbine and pumping mode will be 150 m3/s and
123,7 m3/s, respectively. Also, the power plant will be equipped with 2 reversible
Francis units (2 x 185,5 MW).
The main features of the waterways consist of an upper intake/outlet
structure, upper level headrace tunnel, inclined tunnel upper surge, pressure
shaft, lower level pressure tunnel and penstocks, draft tube tunnels, lower surge
chamber, a tailrace tunnel, and a lower intake/outlet structure. Most of the project
facilities will be underground. The maximum gross head is 285 m and the
distance between reservoirs 6 km.
177
Q. 96 – R. 14
Fig. 4
Salas-Conchas PSP schematic view
Vue schématique du projet de Salas-Conchas
2.3.
EDRADA PSP
Edrada and San Esteban dams are located on the Edrada and Sil Rivers, in
North -Western Spain near the city of Orense. Edrada dam is owned by GNF.
Edrada reservoir contains an operating volume of 10,5 hm3. Edrada dam is
a concrete gravity type dam 37 m high above foundation. On the other hand, San
Esteban reservoir contains an operating volume of 213 hm3. San Esteban dam is
a concrete gravity type dam with a height of 115 m above foundation.
Fig. 5
Edrada and San Esteban dams
Barrages d’Edrada et de San Esteban
Maximum flow will be 150 m3/s in turbine mode and 115 m3/s in pumping
mode. The project will have three identical reversible groups installed in the
power house (3 x 255,7 MW).
The main features of the waterways consist of an upper intake/outlet
structure, upper level headrace tunnel, upper surge chamber, pressure shaft,
178
Q. 96 – R. 14
lower level pressure tunnel and penstocks, draft tube tunnels, a short tailrace
tunnel, and a lower intake/outlet structure. The waterways length is
approximately 5 km, for a gross head of 585 m.
Fig. 6
Edrada PSP schematic view
Vue schématique du projet d’Edrada
3.
ADVANTAGES OF USING EXISTING RESERVOIRS
Environmental constraints dictate that GNF should use existing dams and
reservoirs to develop new pumped storage projects, but there are other
considerations to be analyzed. Obviously, the main reason to use existing
reservoirs is to avoid the erection of new dams and the associated lakes has
been the first premise in the identification and development of new PSPs by
GNF. Avoiding the construction of new dams optimizes the costs and also
prevents from the main environmental and social.
The drastic saving that implies the use of existing reservoirs allows
increasing the value of the ratio L/H that makes the project economically
feasible.Other advantages are the presence of existing transmission lines and
access roads in the surroundings areas of the reservoirs, has allowed the use of
these facilities by the projects, reducing not only the environmental impact, but
also the costs and the magnitude of the works.
179
Q. 96 – R. 14
The quarries used for the dams construction which are currently
abandoned, could be employed as a landfill for the materials coming from the
excavation of the new projects. Also the restoration of the topography and
landscape to their original state with these materials gets the recovery of the
degraded areas.
The location of the intakes in the reservoirs is important, because has to
meet a compromise between the optimal layout of the waterways between the
reservoirs, the minimum depth required by the intakes (defined by the
submergence, the regulation volume needed for the pump – turbine cycle) and
constructive considerations (access, reservoir level descent needed for the
construction). Moreover, the intakes could be constructed using the dam, for
example, drilling the core dam.
The fluctuating level of the reservoirs has to be analyzed. First because is
necessary to determine the gross head and consequently calculate the capacity
and energy of the projects. Then, because this action can cause media and
social conflicts related to negative effects on tourism, for example in pears, river
beaches, fishers...
In conclusion existing dams could be a great choice to implant Pumped
Storage Projects to meet sustainable criteria for grid stability and reliability.
SUMMARY
GNF is developing several Pumped Storage Projects using existing dams
and their reservoirs to store energy produced from other sources, as wind or
solar, into potential energy and afterwards, turbine to obtain electric energy when
needed. Three of the new PSPs in North- Western Spain are: Belesar III, SalasConchas y Edrada.
The main reasons to use existing reservoirs are: optimize the costs,
prevent from environmental and social impacts, optimize use of existing dams
and reservoirs.
RÉSUMÉ
GNF développe plusieurs STEP utilisant des réservoirs existants pour
stocker l'énergie produite à partir d'autres sources, telles que les énergies
éolienne et solaire, sous forme d’énergie potentielle avant turbinage pour obtenir
de l'énergie électrique en cas de besoin. Trois nouvelles STEP sont prévues
dans le Nord-Ouest de l'Espagne : Belesar III, Salas-Conchas et Edrada.
180
Q. 96 – R. 14
Les principales raisons d’utilisation des réservoirs existants sont:
optimisation des coûts, réduction des impacts environnementaux et sociétaux,
optimisation de l'utilisation des barrages et des réservoirs existants.
181