Balancing green power : how to deal with variable energy sources /: how to deal with variable energy sources. (2016)

• Record Type: Book
• Further Information: Note: David Elliott.
• Authors: Elliott, David, 1943-
• Contents: 1. Introduction: balancing variationsRenewable energy sources are large but some are variable and intermittent. The use ofvariable sources for energy supply will require some way of compensating for this variability.Power grids already balance variations in conventional energy supply and variations inenergy demand and the approaches used for this can be expanded to deal with renewablesup to quite high levels of renewable penetration. The main current option is to use fossilplants to back up renewables. However at higher levels of renewable penetration, other, additional, balancing mechanisms may also be needed, including energy storage, smart griddemand response and supergrid imports and exports. This introductory chapter outlines theoptions, which are then explored in more detail in the rest of the book.2. The story so far: balancing with fossil plantsFossil fuel-fired power plants are used to balance variations in grid energy supply andvariations in demand, by ramping output up and down. Some types of modern gas firedplants can do this rapidly and with relatively low efficiency losses. With renewables on thegrid, they would have to do this more often, imposing a small extra cost and leading to asmall reduction in the carbon emissions avoided by using renewables. The latter can beavoided by using green energy sources to fuel the gas plants, but there may be limits to howmuch green gas will be available. In principle, gas plants can provide balancing for bothshort-term variations and long-term lulls, using stored fuel. Nuclear plants may not be ablebalance short-term variations but might play a role in dealing with long lulls. Some types ofrenewables are less variable and can play a role in short and possibly longer term balancing, but fossil plant backup remains the most popular and cheapest option at present.3. The next challenge: energy storageEnergy can be stored in a variety of ways and at various scales for both the short and longterm. Smaller scale short-term options include batteries, longer term bulk storage optionsinclude pumped hydro reservoirs. Energy storage is generally expensive, but provides away to deal with surplus outputs from renewable energy generators, enabling the excessenergy to be used later, when there is lull in renewable output and/or a rise in demand.Storing gas and heat is easier than storing electricity, so it may be best in some situations toconvert electricity generated from renewable sources into heat, liquid air or synthetic gasses, although there will be conversion loses. Solar or biomass generated heat can be storeddirectly for subsequent use in meeting heating needs at various scales. Larger systems areusually more cost effective, as is true for most forms of storage, but some domestic-scaleoptions may be viable.4. Grid links to the futureRenewable energy availability varies by time and location, so one way to deal with this is totransmit it from where it is available to where it is needed. That is what is already done withfossil gas, and sometimes also, over shorter distances, with heat. Renewable heat and gassupplies can be treated in the same way. So can renewably generated electricity. Electricitytransmission by high voltage AC grid links is widely utilized, but it's not as efficient over longdistances as transmission using high voltage DC. HVDC supergrids can be used to balancelocal variations in renewable supply and local energy demand across whole regions orcontinents, making use of geographically-defined weather-related variations in availability. Inaddition to long distance trading of local surpluses, it is also possible to use smart gridsystems, perhaps in conjunction with variable �time of use� pricing arrangements, to managevariable demand and supply, by delaying demand peaks via temporary disconnection of highloads.5. System integrationThe various options for grid balancing looked at so far all have pros on cons. No one singleoption seems viable across the board. Studies have attempted to ascertain what the optimalmix in technical, environmental and economic terms might be in a variety of contexts. Thischapter reviews some examples of such studies covering potential interactions, conflicts andtrade off amongst candidate options. For example, the availability of supergrids wouldreduce the need for storage and vice versa. It may also be, as one study asserts, that eventaken together, storage, smart grids and supergrids may not be enough to avoid continueduse of fossil backup or reliance on nuclear energy. The final likely, or best, mix of balancingoptions is thus still open to debate and will of course depend on what supply mix emerges.6. Conclusions: making changesAs the use of renewables expands, it has become necessary to provide grid balancingfacilities. This final chapter looks at how this type of development has been promoted, focusing on the different market- based approaches being adopted in the UK and Germany.It is far from clear which the best approach is, but it does seem clear that as renewablesdevelop the emphasis will move away from large baseload plants to more flexible energysystems both for supply and demand management. That transition is currently uneven, inthat, for example, unlike Germany, the UK for still supporting large centralised nuclearprojects. Whether that approach will avoid balancing problems is far from clear. But theflexibility concept would suggest that it will not. More likely a shift to new more decentralisedsupply technology will become the norm and will require a shift to new balancing technology.In which case we need to decide on the right mix and ensure that it is ready.
• Publisher Details: Bristol : IOP
• Publication Date: 2016
• Extent: 1 online resource, illustrations
• Subjects: 621.042; Electric power production -- Forecasting; Electric power distribution; Renewable energy sources
• Languages: English
• ISBNs: 9780750312301; 9780750312325
• Related ISBNs: 9780750312318
• Notes: Note: Description based on CIP data; item not viewed.
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