Local Energy: Distributed generation of heat and power
In the future, the UK's energy supplies, for both heat and power, will come from much more diverse sources. In many cases, this will mean local energy projects serving a local community or even a single house. What technologies are available? Where and at what scale can they be used? How can they work effectively with our existing energy networks? This book explores these power and heat sources, explains the characteristics of each and examines how they can be used.
Inspec keywords: cogeneration
Other keywords: distributed power generation; distributed heat generation; local energy projects; power sources; UK; CHP; heat sources; local energy supplies; energy networks
Subjects: Distributed power generation; Thermal power stations and plants
- Book DOI: 10.1049/PBPO055E
- Chapter DOI: 10.1049/PBPO055E
- ISBN: 9780863417399
- e-ISBN: 9780863419904
- Page count: 208
- Format: PDF
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Front Matter
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1 Developing the UK's energy infrastructure
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This chapter discusses the energy infrastructure in the UK. In other countries in the late 1990s, an alternative model for electricity generation was being explored that went right back to the UK's early electricity industry. Countries where there was no electricity infrastructure already existing were developing one that looked rather like the UK's early industry, with local electricity generation for local use, and gradual linkages forming betw een local areas to exchange supply and supply backup where necessary. Neither the UK's privatized system nor its power market supported this type of local generation. By 2000, it was clear that government intervention would be needed to change the market structure to force it to invest not only in new types of generation such as renewables, but also to shift the balance in the UK away from a centralized system so that electricity could be generated at whatever scale and site it was most efficient. That would mean that, as well as central power stations, there would be electricity fed into the system from a huge variety of local projects 'embedded' into the lower-voltage parts of the network. It could make the network more efficient, more reliable and cheaper to operate, but it would clearly require government intervention and financial incentives to make the shift.
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2 The electricity system
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The UK's electricity supply system works in much the same way as the supply of any other commodity. Electricity is 'manufactured' at power stations, and bulk supplies are transported across the high-voltage transmission network. Retailers ('suppliers') buy the bulk power and sell it on to domestic and commercial customers, to whom it is supplied via a low-voltage local network operated by a distribution network operator (DNO). The generators, high-voltage network operator (National Grid), DNOs and retailers are very different companies.
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3 The heat connection and cogeneration
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This chapter discusses the electricity supply industry of UK.
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4 Wind power
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Wind turbines are becoming a familiar sight, both as large wind farms and singly, as here. So far, wind has been the most visible form of embedded generation, as small-scale wind farms have been developed across the UK in the last five years. But wind power has many other guises that make it fit a variety of embedded generation needs, from single houses to large industrial users.
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5 Hydropower
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Water power has been a familiar sight for thousands of years. Most people in the UK probably know an old water mill, whether or not it still has its water-wheel that has been converted to another use, but the water that powered a threshing machine or grindstones can be used equally well to generate electricity.
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6 Marine renewables
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So-called marine renewables encompass devices that tap the energy of either tides or waves. The term is also used sometimes to refer to offshore wind as they share some development issues, such as making the equipment sufficiently robust to withstand the marine environment or transporting the power from an offshore generation site to the users on land. This chapter focuses on the wave and tidal sectors.
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7 Solar photovoltaics
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This chapter discusses photovoltaics for generating electricity from solar energy.
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8 Combined heat and power
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A common method of generating electrical power involves a process known as the Rankine cycle. A working fluid (often water) is placed in a system at high pressure and is passed through a boiler The fluid is heated, but, because of the high pressure, it does not boil but instead becomes 'superheated'. The superheated liquid is then expanded through a turbine, which it turns to produce electrical power. The resulting gas is then condensed into a liquid and returned to the circuit. The process produces electricity, but most of the heat generated to drive the process is wasted for power stations dispersing this waste, heat is a real problem and requires cooling towers or large heat sinks such as rivers or the sea, but heat is a basic requirement for both industrial and domestic uses. In fact, some 40 percent of the UK's energy requirement is for heat. Using the heat from the power station, for example by piping hot water to local homes and businesses in a district heating scheme, makes very little difference to the operation of the power station but can increase the proportion of the fuel that is transformed into usable energy from 30-40 percent to upwards of 80 percent.
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9 Biomass
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This chapter discusses biomass fuel which comes from wood, which is the oldest and still has an important role to play. Wood has provided heat for millennia, but only recently has modern technology increased efficiency and automation. In northern Europe and North America, wood burning technology is widely used and markets are large and well developed. In northern Europe, medium-sized, automated central-heating systems underpinned by capital-grant schemes were used to develop the markets, after which large-district heating, combined heat and power (CHP) and power schemes were built. Wood now accounts for up to 40 percent of space heating in rural areas in some countries. Britain's Forestry Commission exports timber for this purpose. The Commission recently supplied 2 000 tonnes of timber via a merchant from its North York Moors forests to Denmark for use in wood-burning power plants. Virtually any form of biomass can be considered for fast pyrolysis. While most work has been carried out on wood due to its consistency, and comparability between tests, nearly 100 different biomass types have been tested by many laboratories ranging from agricultural wastes such as straw, olive pits and nut shells to energy crops such as miscanthus and sorghum, forestry wastes such as bark and solid wastes such as sewage sludge and leather wastes.
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10 Energy storage
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This chapter discusses energy storage.
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11 Fuel cells
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Fuel cells can provide heat and power, and a huge variety of fuel-cell devices currently being tested and demonstrated are likely to hit the market in the next decade.
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12 Interacting with the electricity grid
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Managing the electricity supply across the grid is not simply a case of generating enough electricity to meet the needs of all the customers connected to it. Wherever customers tap into the power network it has to be able to supply power that has well defined characteristics and that is supplied with minimal disturbances or interruptions. What is more, the quality of the grid supply has become still more important as customers at all scales from the domestic to heavy industry use electronic equipment that can be sensitive to disturbances in the supply that last a fraction of a second.
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13 Making progress on policy
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The need to rethink the UK's electricity network to accommodate local energy projects was already exercising the minds of the industry at the start of the new century. In 2001 Galium McCarthy, then chief executive of the regulator, the Office of Gas and Electricity Markets (Ofgem), said that government targets on renewables and CHP would require the biggest revolution in the distribution network for 50 years. He told distribution network operators (DNOs) they must 'bring these issues to the top of the senior management agenda' and said that for Ofgem, too, it was 'emphatically not business as usual. Today, a DNO might have 300 embedded generators within its entire network. If the government's targets are to be met, by 2010 a DNO could have 300 generators connected to every substation.'. Even then, he said, meeting the 2010 targets 10 per cent renewable generation and 10 GW of CHP would require 3 000 new renewable installations, 1,000 CHP plants and up to 3 million domestic CHP installations. Technically, passive local networks would have to become active managers and, financially, DNO investment planning would be more demanding and take on more commercial dimensions.
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14 Embedded benefits
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Generators and electricity suppliers (retailers) directly connected to the electricity transmission grid pay a series of charges for using the network that can be avoided bv using local generation.
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15 Connecting and exporting power
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How do you export power from your local energy installation to the electricity grid? Until recently, connection was a notoriously complex business, depending not only on your installation and whether you hope to get some income from the export, but also on regulations that were intended for very different electricity generators and distribution network operators (DNOs) whose procedures and attitudes vary widely. However, a new connection standard designed for the job has simplified matters considerably, as have new regulations that determine the price paid for the connection and that will force DNOs to offer export tariffs to new generators. At bottom is a new attitude that acknowledges that, rather than being a nuisance or a sideshow, local energy projects can strengthen existing energy-supply arrangements, reduce the need to make expensive reinforcements to the grid when new demand in the form of new housing or business arrives in the area, introduce efficiency and persuade people to use energy with more care.
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16 Finance and local generation
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The capital cost of local power and heat projects is often rather higher than providing power or heat conventionally. There are a number of reasons for this: the equipment is relatively new or supplied in small volumes, so it is more expensive; the technology may be new to its location, so alterations are required in existing buildings to allow for it; it may simply have had a different cost structure from more conventional choices, with high capital costs eventually balanced by low operating or fuel costs. The government response has been to try to pump-prune the market with subsidies and grants that will eventually increase the market size to a point when unit costs begin to fall. That effort has been made more difficult because the options for distributed energy are so varied and apply at such different scales. Developing a volume market for the domestic scale is probably more achievable than it is at mid-scale, where energy will always have to be tailored both to the resources available and to the particular needs of the customer. One problem at mid-scale is that companies often require payback on new capital investments within a few years. A switch to so-called life-cycle costing, whereby the purchasing and installation costs are assessed in conjunction with fuel and maintenance and often removal at the end of the plant's lifetime is more likely to favour distributed energy.
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17 Changing the industry: ESCos and cooperative power ownership
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At the moment, energy customers buy gas and electricity from their energy suppliers. But electricity and gas are not what they really want: in reality they want services such as heat, lighting, refrigeration or entertainment. Energy-services companies (ESCos) can operate to take advantage of the mismatch between what customers are buying now and what they really want. In the process, it is hoped that providing services rather than energy could make it possible to make big energy savings - not least because for most customers energy is an alien concept. That means it is perceived as complicated and of dubious benefit to make energy savings - customers want to be sure they will have the services they want, and are not necessarily convinced that that can be achieved if less energy is used.
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18 Output and generation
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No form of generation will generate power or heat continuously. This variability in generation sources is of benefit to grid operators, because it means that there are a number of options available to balance supply with demand as it varies during the day, the week and the year. A diverse electricity supply industry with a variety of sources of electricity supplying the industry at different scales is the most robust. Utilities use the term load factor to compare the different outputs of power generation plants. Load factor is generally the amount of power produced by the plant compared with its theoretical maximum output, but this may also be referred to as 'capacity factor', implying that it measures how much of its total capacity the plant is supplying.
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19 Putting a price on carbon
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The European Commission's emissions-trading scheme should impose a cost on energy generators that produce carbon dioxide, favouring renewable generation. In July 2005, Greenpeace set out a list of changes that would have to be made to support and encourage DG in the UK. Among its proposals were changes to building regulations that would ensure that distributed energy was used in new homes and business premises, changes in the rules on network access and export tariffs that would support the export of excess power from small generators, and tax changes that would give a financial incentive for installing distributed energy. Progress in some of these areas has been significant, as is described elsewhere in this book. Many believe, however, that all progress on distributed energy must be underpinned, and will be given much more impetus, if the effect of carbon dioxide emissions is fully assessed and costed. Greenpeace raises this possibility in its wish list as a tool to make visible the effects of carbon dioxide emissions from large fossil-fuel-generating stations and impose a financial penalty accordingly, but many believe that 'discovering' a price for carbon dioxide emissions will be fundamental to shifting the balance of our energy industry. When the price of carbon dioxide emissions is factored into the energy price, it should reward companies and individuals who switch to the most efficient forms of energy generation, as well as those who use sources that, like renewables, do not produce carbon dioxide emissions.
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Back Matter
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