During my meeting with boffins last week, when I raised the thorny problem of how many new power generation plants the UK would need to build if all home heating and personal transport were shifted to electricity – and then how they would be left idle for most of the year – my conversational correspondent said it really wasn’t a problem – gas-fired power plants are cheap to build, and they wouldn’t be consuming gas when they’re resting. I found this position untenable – as it could well mean gross inefficiencies in the use of energy, besides locking capital up in unused and unsuable plant. The person asked whether I was after optimising cost or efficiency in energy systems, and my reply was “both”.
After putting together a basic power consumption profile, I realised I needed to build a basic heat model as well, in order to test various simple options of how to meet demand. This proved even harder than the electricity model, as I couldn’t find representative heat demand data of any quality – or at least, I haven’t found any yet. I had to invent a seasonal/weekly half-hourly heat demand profile in order to be able to compare gas demand data to electricity demand data. I must admit, it was extremely basic. I then calculated half-hourly non-industrial heating demand and half-hourly industrial gas demand for 2014. The industrial gas demand would partly be used for generating electricity, as can be seen in the rise and fall in demand maxima when charted alongside power consumption – however this chart is poor, as it slips into the negative, showing that I don’t have any data for half-hourly gross gas demand in the UK, and I’m just using a daily figure divided equally into 48 segments, which is clearly not good enough.
I need to improve this model and then test various options for supplying heat demand.
Some examples of efficiency issues :-
1. Converting primary energy to energy as supplied to consumers
Much centralised power generation in future will be gas-fired, and this is something like 60% efficient – 40% of the energy in the gas is lost as heat.
2. Delivering supplied energy to consumers
I don’t know good figures, but is likely that transmission losses for electricity are much higher than for gas.
3. Gas-fired central heating compared to heat pump heating
Heat pumps that take their input energy from supplied electricity may be on average far more efficient than gas-fired central heating, but heat pumps that rely on gas as the input energy might be a better option.
4. Centralised gas-fired power generation compared to localised Combined Heat and Power (CHP)
By far the most important source of potential future energy efficiency is the relocation of centralised power generation to the local area where the heat may be used for District Heating (DH). Heat demand is currently roughly an order of magnitude larger than power demand. There are many options for developing the use of CHP/DH, in combination with other heating options, such as heat pumps, thermal stores and manufactured Renewable Gas (as an energy store). It remains to be seen if it would be more efficient to run CHP plant to cater for most of the large heat demand and supply the byproduct electricity to manufacture gas, or heat pumps for the rest of the heat; or run the CHP plant only for small local electrical power needs (where there are not many heat pumps), and use the byproduct heat for storage in thermal stores (the DH pipeline network, for example).
The reason why efficiency is absolutely crucial is that within 30 years’ time there could well be problems with guaranteeing reliable and ample supplies of Natural Gas. If gas options for energy are generally more efficient than power options – and especially if gas will be the source of much electricity – we will need to have gas-heavy technology choices, and develop indigenous supplies of manufactured and biological Renewable Gas.