Useful links and info

Reducing the cost of system intermittency using demand side control measures


In 2006, Flexitricity participated with IPA Consulting and Econnect in a wide-ranging study of intermittency in an electricity system.  The study considered

  • The environmental and financial costs of balancing supply and demand;
  • The effect of growing demand and renewable generation on these factors;
  • The size and shape of the contribution which demand-side flexibility could make.

The broad conclusions were:

  • Demand-side flexibility can reduce national electricity-sector emissions of carbon dioxide by between 300-750 tonnes per annum for each megawatt of flexibility provided;
  • Pumping, air-conditioning, refrigeration, standby generation, CHP and hydro generation can each contribute volumes of flexibility which are as large as power stations;
  • The need for demand-side flexibility will grow very substantially as the generation mix shifts from coal, oil and gas to renewables and nuclear.

The study was supported by the UK Department of Trade and Industry (now the Department for Business Innovation and Skills).

Reducing the cost of system intermittency using demand-side control measures Download the full report here.

 

Tea-time Britain

Part of the BBC's “Britain from above” series, “Tea-time Britain” is a five-minute clip showing how electricity supply and demand are kept in balance in real time. 

By chance, the BBC was present in National Grid's control room at just the right moment to show what happens when things go wrong.

This clip may not be available outside the UK.

 

Flexible CHP with anaerobic digestion

This DTI Global Watch Mission Report contains many examples of community-owned electricity generators.

Section 6 describes a district heating scheme with many environmentally positive flexible features:

  • The fuel is pig slurry, collected from neighbouring farms.
  • A pasteuriser and an anaerobic digestor are used to treat the pig slurry.  The anaerobic digestor creates biomethane.
  • Two combined heat and power (CHP) engines burn the biomethane to create electricity.
  • Heat from CHP engine cooling water and exhaust gases is used to warm the anaerobic digestor and to feed the district heating network.
  • A gas holder, which stores biomethane, and a hot water heat store, allow the plant to operate flexibly, allowing slurry treatment, heat supply and electricity generation to be partially decoupled.

The flexibility in the design maximises the revenue from renewable electricity generation, while keeping the treatment process running continuously and ensuringthat the plant misses no opportunity to generate clean heat.

 

Triads

The “triad” system is the means by which industrial and commercial electricity consumers pay for the electricity transmission network in Britain.  The triad system doubles up as a peak load management mechanism.

Our white paper on triads is available in downloadable form; please click here to view.

For additional information visit National Grid's explanation of triads.

 

Real-time GB electricity market information

A real-time view of the GB electricity system has been provided by Elexon, the company responsible for the GB electricity balancing and settlements infrastructure.  This page shows demand, margin, generation mix and a variety of other data.

It is also possible to track the activities of large power stations, or “Balancing Mechanism Units” (BMUs).  To use this page, you will need National Grid's list of licensed power stations.

Utilisation of Short Term Operating Reserve from sources other than large power stations, including Flexitricity, can be viewed on the STOR non-BM instructed volumes page.  Please note that the data shown here are in MWh total instructed in each half-hour.  The actual MW generation or load reduction can be estimated by doubling the MWh figure.

 

Renewable energy and electricity system balancing

If a large fraction of electricity generation comes from renewable sources, how can the electricity system be kept in balance?  This question has been addressed by many research groups, and a large body of information is available.

Most research deals with wind generation.  You can see real-time wind generation data amongst other sources on Elexon's Balancing Summary Page; the fuel-type table is updated every five minutes. 

Please note that this only covers around one third of the wind farms connected to the GB system.  The remaining two-thirds of total wind generation is counted as negative demand.  For a very rough view of the instantaneous total wind generation, simply multipy the generation shown by three. 

Some other sources of information are:

Most research on renewable energy balancing acknowledges several key points:

  1. Generation capacity is not the same as fuel consumption.  Wind power can reduce fossil fuel burn without necessarily reducing the amount of fossil fuelled generation capacity available.  See David Milborrow's article and the University of Edinburgh study.
  2. Predictability is valuable, even though it is not the same as controllability.  The more accurate and long-range the prediction, the less fossil fuel is wasted in keeping capacity available.  The study by IPA, Econnect and Flexitricity addresses this point.
  3. Some forms of renewable generation - biomass, anaerobic digestion, geothermal - are controllable.  Some of these are quantified by the Royal Commission on Environmental Pollution.
  4. Electricity is coupled with other energy uses, including heat and transport.  This is considered by the Royal Commission on Environmental Pollution.

 

Carbon dioxide emissions from electricity generation

Emissions factors

The UK government's method for calculating carbon dioxide emissions associated with burning fuels is contained in the Annexes to the Guidelines to DEFRA's GHG conversion factors.

  • Annex 1 contains carbon dioxide emissions resulting from burning fossil fuels for any purpose.  The kWh factors refer to the heat content of the fuel, not the amount of electrical energy that might be produced from it.
  • Annex 3 contains the method for estimating the carbon dioxide emissions associated with electricity generation.  These are annual averages.  They vary with the mix of fuels used in generation, and the efficiency of the power stations. 

DEFRA's electricity emissions factors do not take account of the continuous, hour-by-hour variations in the carbon content of electricity.  These can be viewed in real time at Elexon's Balancing Summary Page.

Heat rate curves

The efficiency of a thermal power generator tends to reduce as output is turned down below maximum.  This decline is normally shown on the heat rate curve or Willans line. Examples of real and modelled heat rate curves are found at:

 
 
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