Renew On Line (UK) 57

Extracts from NATTA's journal
Renew, issue 157 Sept-Oct 2005

6. Diversity is the Key

'Wind-powered generators and increasing energy efficiency will not meet the White Paper targets on their own.  The projected decline in non-CO2 generation capacity is greater than the feasible increase in existing renewable energy sources up to 2020.’  On the basis of this assertion, in its report ‘An Electricity Supply Strategy for the UK’ the government’s top-level advisory Council for Science and Technology has called for significant investment in low-carbon, large-scale sources of electricity- from tidal to nuclear to clean coal/carbon sequestration- as well as supporting the development energy management systems, including intelligent networks/metering, and electricity storage systems. The Council argues that we need to develop ‘the transmission network, its protection mechanisms and metering systems to facilitate distributed and diverse generators, ranging from commercial to domestic units; and to address the regulatory issues arising from this form of generation’.  It says ‘the long-term advantages of the widespread adoption of small generators will be that (a) diversity and increased security of supply and (b) fluctuations in individual generators (capacity factor) will become less significant when the numbers are large and spatially diverse’.  But it adds that ‘the UK is currently some way from achieving this position’.

A way to go

The Council notes that ‘many renewable sources are currently not often located near to existing power stations or a suitable grid connection. Connecting many small generators to the grid, possibly over long distances, is feasible but carries substantial added costs.  High concentrations of such sources (e.g. a large wind farm) will require upgrading of the grid protection mechanisms to handle local reverse energy flows during periods of peak generation.  There is limited funding available for investment in the transmission network in the short term. In addition to grid issues, it should be noted that most renewables are intermittent and thus require backup capacity if deployed on a significant scale. Such backup capacity will almost inevitably be fossil (gas-fired) because of the flexibility required.  Furthermore, progress to date on delivering renewable generation has not lived up to aspiration, due to issues including planning delays and investor uncertainty.’ 

It concludes ‘For these reasons, it is not possible to meet the challenging CO2 objectives in the medium term without large-scale technologies which do not add to the carbon burden’.  

It sees nuclear power as a possible option, especially since it ‘does not have the disadvantages of poor grid connection or low availability’.  And it claimed that new technology meant that new plants would only add around 10% to the existing waste over a 60-year period. It suggests that a cost effective way to keep the nuclear option open was via participation in international collaborative nuclear R&D programmes, such as Generation IV, which could ‘serve to sustain the UK’s position and influence on new reactor technologies, to contribute to intergenerational transfer of valuable expertise and know-how, and to maintain the UK’s awareness of longer-term energy options’. 

This approach would, it says, only cost around £5m p.a. It also looked to advanced reactor technologies (e.g. high temperature reactors) which it says ‘offer the potential to provide a carbon free energy source for the efficient production of hydrogen, underpinning the potential for a hydrogen economy in the future’.

In parallel, it was keen on Tidal generation, which is sees as ‘another large-scale option, which will add to the diversity of UK generation and reduce CO2 emissions’.  It notes that‘ As robust civil structures, tidal energy barrages would guarantee secure, predictable and sustainable energy supplies, free of atmospheric emissions, for at least 100 years. Although peak generation times would vary throughout the day with the tidal maxima, this could be accommodated because the times are known in advance, some storage can be incorporated, and barrages at different geographical locations have tidal maxima at different times during any 24-hour period. For instance a Severn barrage could provide 6% of the UK’s electricity requirement from an installed capacity of 8640 MW and a Mersey barrage, 0.5% of the UK’s needs. The potential for tidal power was recognised in the energy White Paper and the option left open.  We recognise that any future decision to re-open this area of work would be socially and politically controversial. Therefore any future work should focus first on environmental issues and the financing of such schemes.’ 

 However it also recognises that there are other approaches to tidal power, including tidal current turbines and tidal lagoons, although it claims that ‘a lagoon has significantly higher costs than a barrage owing to the greater length of its retaining wall.  As a result, the generation of CO2 during construction would be higher for a lagoon than a barrier.’ 

 A bit odd that- lagoons would have simple rubble walls and should be cheaper, and, while segmented lagoons can store and phase their outputs, the Severn Barrage would only have around a 25% capacity factor, not 41% as the council say. Nevertheless it recommends that ‘new feasibility studies be carried out for tidal lagoons or marine current turbines as we believe these have environmental advantages over barriers’.

The third main category was Fossil generation with carbon capture. Although the Council admits that geological sequestration has yet to be established as a reliable means of disposal,  ‘opportunities exist for CO2 storage in disused oil and gas reservoirs under the North Sea as well as in some saline aquifers.  Furthermore, CO2 used for enhanced oil recovery (EOR) would offer opportunities not only for CO2 storage but with a payback of recovering oil which might otherwise have been abandoned’.  However it notes that ‘the risks remain high for this option’ and looks to international collaboration in RD&D projects.

The Council laments what it calls the ‘collapse’ of R&D funding since privatisation/liberalisation of the UK energy sector and also says that the Government should engage in dialogue with the public about the different options and should improve the supply and training of the necessary skilled workforce. Overall, a few odd errors on tidal power apart, if keeping the nuclear option open really will only cost £5m p.a., quite a useful document.  It can be accessed at www.cst.gov.uk