User:Mishlai/Intermittent

This page will be used to aggregate sources concerning Intermittent power sources and to maintain notes about their contents for ease of reference.

==Tyndall ==

Length: 52 pages. Subject: Capacity and balancing aspects of renewables in the UK.

General
"Wind power can be generated at wind speeds of 5-25m/second, while the mean wind speed which makes them financially workable is 7m/seconds."

Response to Climate Change
"In the context of reducing CO2 emissions, the UK Government's 2010 targets for Renewables and CHP will make only a small (if symbolically important) contribution. A considerably larger portion of renewable and other low carbon energy sources (e.g. fuel cells, micro CHP and possibly nuclear) will be required in order to respond to the climate change challenge over the longer time horizon." (Intro, p.4)

"The United Kingdom is committed under the Kyoto Protocol to reductions in greenhouse gas emissions of by 2010 of 12.5 percent, compared with 1990 levels, and the Government have also made a national commitment to achieving a 20 percent reduction in the United Kingdom's CO2 emissions by 2010, and a 60 percent cut by 2050. The exploitation of renewable energy sources - abundant and inexhaustible - may assist in controlling emissions... [and] ...meeting its environmental commitments." (p.7)

"The environmental consequences of renewable sources are, virtually without exception, on a much lower scale than for other sources. The most serious effects tend to be aesthetic, such as a reduction in scenic views, and the large number of devices needed to replace the output of a conventional power station resulting in a large area of land being occupied.  Due to their relatively very low intensity of environmental damage and consequent lesser impact on climate change, renewables are foreseen as a significant component of the future energy scenarios." (p.8)

Other env
"The REAG suggest in it its report that increasing use of renewable sources will help to reduce environmental damage caused by acid rains, and limit the emissions of CO2 according to the government commitments." (p.9)

"The main obstacles in this case [offshore wind]] would be: the sea bed must be suitable (water depths less than 40m), construction of the towers and the cables linking them can cause damage to the sea bed, interference with commercial fishing, the dredging of marine aggregates, merchant shipping, military operations, flight paths of birds and visual impact." (p.11)

Wind Dominance
"Our understanding of the analysed medium term projections shows that the wind power can be expected to be a dominant renewable technology by 2020." (Intro, p.4)

"Therefore, it is expected that wind power will play a key role to achieve 2010/2020 targets for renewable generation. However, a considerably larger proportion of renewable and other low carbon energy sources (e.g. fuel cells, micro CHP and possibly nuclear) will be required in the long-term in order to respond to the climate change challenge beyond 2020. (p.6)

Technical Challanges
"This new generation will displace the energy produced by large conventional plant, raising serious questions about the ability of such a system to manage the balance between supply and demand, and hence, to maintain the security of the electricity system." (Intro, p.4)

"Clearly meeting variable demand with intermittent, and/or uncontrolled and/or inflexible generation will be a major challenge for secure operation of sustainable electricity systems of the future." (Intro, p.4)

"Penetration of intermittent renewable resources can displace the energy produced by large conventional plant. However there are a number of concerns in relations to the ability of this new generation to replace the capacity of the conventional plant and in particular its flexibility.  This raises a number of questions as to whether the future sustainable system will be able to operate securely and how exactly the balance between generation and demand will be managed." (Intro, p.4)

"The ability of intermittent sources to replace conventional capacity is investigated ... The question here is how the potential low availability of the renewable resources (such as wind, wave and PV) over a period of several days or weeks would be dealt with in a system with a large contribution to overall electricity supply coming from renewable sources. as this is considered to be a plausible situation and massive load curtailments are assumed not to be acceptable, a significant amount of additional generation capacity will need to be available." (Intro, pp. 4-5)

"Another important question when managing security of decarbonised electricity systems is how to balance their load and generation due to an unpredictable steep increase/decrease in the power provided by intermittent resources or load and sudden loss of generation. Researchers and engineers argue that there will be a need to develop new forms of flexibility in both supply and demand sides in order to satisfactorily manage such situations." (Intro, p.5)

"In a low-carbon electricity energy based system, with intermitent renewable generation producing the vast majority of electricity, considerable capacity of conventional plant may still be required. This would mean the conventional power system might be acting as a backup or standby system, which obviously may reduce the overall value of renewable generation.  Due to a relatively small capacity contribution of intermittent sources a considerable number of conventional plants might be running at low output levels over a significant proportion of their operational time to accommodate this intermittent energy.  Consequently these plants will have to compromise on their efficiency resulting in increased levels of fuel consumption as well as emissions per unit of electricity produced." (Intro, p.5)

Drivers of renewable energy
"...due to a number of issues arising since the last quarter of the last century, the power industry, governments and research and devlopment institutions have started to explore alternative options for electricity generation. Among the key drivers for this new focus were the environmental or climate change impacts and the sustainability of the primary energy sources for the conventional generation technologies.  Besides these two basic drivers, the security of energy supply issue also emerged as being critically important for the smooth operation and development of both the developing and developed economies.  This resulted in an unprecedented interest in renewable technologies that could satisfy the future requirements of electricity production and at he same time be environmentally benign, sustainable in nature and ensure a secure supply of energy." (p.6)

UK
"This [UK] s a windy island, and with the exception of Ireland has the most favourable wind profile, both on- and offshore, in Western Europe." (p.6)

Discussion of UK future dependence on gas imports for electricity, how this affects energy security: p.8

Various info on UK climate change policy and energy makeup & consumption. (p.10)

Energy sector percentages, efficiency measures, portions to transportation & commercial, etc. p.12

Security
"Political risk data provided by the insurance sector suggest that interruptions in such supplies [of natural gas] of up to 180 days may occur as often as once every eight years." (p.8)

"Renewable energy, despite the difficulties it presents to the day-to-day reliability of electricity supplies, has a significant part to play in ensuring long-term security. It is essential that every effort is made to mitigate the effects of intermittency, so that renewables, in enhancing security of supply, do not undermine reliability. (p.8)

More discussion, including the value of diversity and that the presence or absence of nuclear affects this. p.8-9

Nuclear
"Nuclear power is the only major source of electricity which could, in theory, be used in all countries on the scale of fossil-fuelled power stations and which does not emit carbon dioxide. However, unfortunately, as the Chernobyl accident demonstrated nuclear power also has the capacity for large scale contamination.  While the standards of engineering and the safety requirements of nuclear power plant in the UK are exceedingly high, there is no doubt that the spectre of Chernobyl in the former USSR is the dominant force affecting public opinion.  Secondly, the issue of managing the highly radioactive spent fuel is still open.  This discourages the future large scale role of nuclear technology." (pp.7-8)

Cost
"The SCAR report investigated a number of possible scenarios showing that extending renewable generation to 20% or 30% of demand by 2020 would increase system costs associated with integration of this generation in the UK power systems. The extent of the additional system costs was found to vary considerably, depending on the technology and location of renewable plant.  An analysis of the breakdown of the total costs, between the three elements examined - balancing and capacity, transmission, and distribution, demonstrated that balancing and capacity costs, principally the cost of maintaining system security, dominate all other costs.  These costs arise because of the intermittency of many renewable technologies, in particular wind..." (p.9)

Other renewables
"Photovoltaic cells efficiency in converting sunlight energy into electricity is about 20% in research devices, but not more 11-15% in practical devices. The main obstacles to using this technology on a large scale are the high cost of the cells and ancillary equipment, 25-30 years life cycle, and a very low efficiency." (p.11)

Some discussion of CHP and wave/tidal on p.12