Frequency (Hz) Figure 11.1 Operation of the Dynamic Demand concept
energy capacity can be absorbed without the need for additional frequency regulation.
Barrett's work in progress, reported in Chapter 9 of this volume, suggests that up to 95 per cent of the UK's electricity supply could be met from renewable sources. Similar conclusions were derived in research completed at CREST by Streater (2002), which also used hour-by-hour modelling of the aggregated UK electricity load and renewable supplies. Both studies ignored the detail of geographical distribution and related connection and transmission issues, although the positive contribution from the geographical diversity of the renewable energy supplies has been incorporated, to an extent, within Streater's (2002) study. There are some significant differences in the assumptions, most notably the inclusion of CHP in Barrett's study.
Figure 11.3 is reproduced from Streater (2002) and shows the hour-by-hour contributions from the different renewable energy sources and their aggregate compared with both the electricity (power) load and the aggregate heat and electricity load. The term 'source-load' is the surplus of supply over aggregate load and shows that for only about 12 weeks in the year is there an energy shortage, and also that for large parts of the year there is a significant energy surplus. In Barrett's model, this surplus is stored for future use. Whether this is attractive will depend upon the cost of energy storage; it may well be cheaper and simpler, overall, to curtail the output from the renewable devices. Note that in Streater's (2002) work, the combined renewable output far exceeds the electrical power demand throughout the year.
Of course, it may well be that energy storage appears in the system for other reasons. As discussed by Barrett (see Chapter 9), it may well be that a significant proportion of transport needs will be provided by electric vehicles. Whether these are powered by batteries or fuel cells is immaterial if the energy is supplied by the electricity system. In both cases, substantial energy storage is involved and this can be used to improve the utilization of the renewable resources. In fact, this storage may be essential for stable dynamic operation of the electricity supply system, and this critical issue is not addressed in either Barrett's (see Chapter 9) or Streater's (2002) studies.
Micro-generation (i.e. very small, ideally renewable, source-driven generators located on consumers' premises) is of increasing interest. How this develops in practice is currently unclear and will depend upon the economics relative to larger renewable energy installations, such as wind farms. This development may well ease the technical electrical integration issues since the generation will tend to be nearer to the loads; but it should not substantially affect the aggregated results presented here.
One of the challenges in delivering the developments discussed - in particular, extensive demand-side management and high levels of distributed generation - is to reward the participants. This may require adaptation of the existing market system. The present arrangements under BETTA allow for a balancing market where flexible generators and suppliers can bid/offer to change their positions at short notice. As mentioned above, this can provide significant financial returns to those players in the market who have sufficient flexibility. However, playing such a market needs investment in the appropriate
Source: adapted from Streater (2002)
Figure 11.3 Hour-by-hour variation in renewable energy generation over one year, compared with variations in energy requirements
Source: adapted from Streater (2002)
Figure 11.3 Hour-by-hour variation in renewable energy generation over one year, compared with variations in energy requirements information technology (IT) systems and dedicated trading teams. The present balancing market in the UK was designed for the major market players who can afford such investment. Smaller players, such as householders, small commercial companies and small embedded generators are not able to participate in such a market. First, they are at a level where their consumption is not metered half hourly; and, second, the value of adjusting their output individually would be less than the cost of the metering and associated IT systems that would be required for active participation. Besides, few small consumers or generators would have the time or resources to play the balancing market. The system would need to be changed substantially to allow household-level demand-side management and embedded generation to benefit from such a market. This would require low-cost smart metering and automatic systems driven by market price signals, which would necessitate little or no user intervention, possibly coordinated by the contracted electricity supply company. The supply company could then aggregate the benefits for a number of small consumers or generators and pass on the associated benefits. Such changes could open up a significant market for small-scale flexible demand and generation, and provide further flexibility to the system operator, which could aid the process of integrating variable renewable energy sources within the grid.
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Global warming is a huge problem which will significantly affect every country in the world. Many people all over the world are trying to do whatever they can to help combat the effects of global warming. One of the ways that people can fight global warming is to reduce their dependence on non-renewable energy sources like oil and petroleum based products.