Preparing the UK Electricity Network for Rising Cooling Demand

I'd definitely think that our first step should be towards preventing overheating in the fist place - there are plenty of means for shading south facing windows and so on and many features of "modern designs" for keeping heat in (insulation and controlled air flow) should be at an advantage when it comes to keeping heat out too. "Active cooling" should be the last resort - but I agree it will increase and the problem needs examining.

The next question is how high would the demand for cooling be? At a first guess we might want to keep the house at maybe 10-15 degrees cooler than outside - compared with perhaps 25-30 degrees warmer in winter. Given that there are already plans to shift from gas to electric (mainly heat pump) heating, it might be that summer cooling demand would be less than winter heating demand as far as the grid was concerned.

There are perhaps two sides to the national grid - generation and transmission/distribution. On the transmission side, things have to be built for maximum demand - so as long as the summer cooling isn't larger than the winter demand, no additional capacity should be needed. Generation though is another matter. We tend to have "heat waves" under unusually large and static high pressure systems - which means winds are low - so wind based generation capacity may well not be sufficient. Solar is the obvious counter-balance - but still some thought as to the overall balance between generating (and storage) technologies to cover situations throughout the year may be needed.

   - Andy.

I'd definitely think that our first step should be towards preventing overheating in the fist place - there are plenty of means for shading south facing windows and so on and many features of "modern designs" for keeping heat in (insulation and controlled air flow) should be at an advantage when it comes to keeping heat out too. "Active cooling" should be the last resort - but I agree it will increase and the problem needs examining.

The next question is how high would the demand for cooling be? At a first guess we might want to keep the house at maybe 10-15 degrees cooler than outside - compared with perhaps 25-30 degrees warmer in winter. Given that there are already plans to shift from gas to electric (mainly heat pump) heating, it might be that summer cooling demand would be less than winter heating demand as far as the grid was concerned.

There are perhaps two sides to the national grid - generation and transmission/distribution. On the transmission side, things have to be built for maximum demand - so as long as the summer cooling isn't larger than the winter demand, no additional capacity should be needed. Generation though is another matter. We tend to have "heat waves" under unusually large and static high pressure systems - which means winds are low - so wind based generation capacity may well not be sufficient. Solar is the obvious counter-balance - but still some thought as to the overall balance between generating (and storage) technologies to cover situations throughout the year may be needed.

   - Andy.

I agree that passive cooling should always be the priority. Improving shading, external blinds, reflective roofing materials, natural ventilation, and designing buildings to minimise solar heat gain can significantly reduce the need for mechanical cooling while also improving energy efficiency.

Your comparison between winter heating and summer cooling demand is an interesting one. Although the average cooling load may be lower than winter heating demand, there is still a concern about the timing of that demand. If many households begin using air conditioning simultaneously during short heatwaves, distribution networks could experience high local peak loads, particularly in residential areas that were not originally designed for significant summer electrical demand.

I also agree that generation presents a separate challenge. Heatwaves are often associated with low wind speeds, which can reduce wind generation output. Fortunately, peak cooling demand generally coincides with high solar irradiance, so photovoltaic generation could help offset some of the additional demand. The remaining challenge is ensuring there is sufficient energy storage, flexible demand management, and local network capacity to balance periods when renewable generation and demand are not well aligned.

This is why I think the issue deserves attention now not because cooling demand has already become a major problem, but because planning for future network resilience is generally more cost-effective than reacting once widespread adoption has occurred.

If many households begin using air conditioning simultaneously during short heatwaves, distribution networks could experience high local peak loads, particularly in residential areas that were not originally designed for significant summer electrical demand.

Would the same not be true of heating loads during a cold snap? (especially once heat pumps have generally replaced gas/oil boilers)

   - Andy.

It will, and perhaps the question can be better framed, "how do we prepare the electrical grid to have the capacity to meet future demand and also replace the gas network?" 
The most enthusiastic proponents, expect the gas to be empty and decommissioned by 2050 or so! 

My money would be on slightly later, but even so that is likely to be well within the life of the supplies and wiring of all houses being built now and indeed plenty already built.
At the moment most houses have a 20kW or higher power gas boiler for water and heating, though more care and control of heat losses may mean something smaller can be used if converted to electricity.
Even so, just adding half that at extra 10kW per building would be a massive change to the load patterns.

For sure cables are more stressed in summer, so the ability to ride-out what might be otherwise a small overload is better in winter.  More explicit use of temperature dependant ratings may be needed.

If demand rises we may need to look at 3 phase in a domestic setting and  supplies within larger buildings such as blocks of flats may need conversion to  higher voltages beyond a certain point - it may become cost effective to use transformers rather than heavier cables.

Years ago I was very impressed by how much power could be sent how far by 630V/1k3 three phase in a German factory, compared to what would have been UK practice of having a very beefy 230/400 cable - this sort of thing may need to be considered more here.
Mike.

Mike

mapj1 said:

At the moment most houses have a 20kW or higher power gas boiler for water and heating, though more care and control of heat losses may mean something smaller can be used if converted to electricity.
Even so, just adding half that at extra 10kW per building would be a massive change to the load patterns

I don't think gas boiler power ratings will be a good guide to electrical demand, firstly because the highest boiler powers are for instant hot water heating Combi boilers, whereas electric hot water heating either uses lower powered elements combined with storage, (i.e. 3 kw immersion in a cylinder), or heat-pumps with a cylinder (2 kW input?) or short-duration appliances like a shower (max 10kW) but which have high diversity across a neighbourhood.

For the space heating, the boiler demand after diversity, at the neighbourhood level, is limited by household heat loss. Most households have heat losses well below 20kW, so in practice the boiler is either cycling on-off, with a lower time-averaged power demand, or for modern modulating boilers will be running at something around house heat loss. 

When the space heating load is moved over to heat pumps, with CoPs of around 2-3 under worst case conditions and sized for house heat loss, the heat demand might be 8-10kW, with an electrical demand more like 3-5kW under worst case conditions. 

I suspect the key issue will be getting households to use the available generation and network capacity efficiently, to engage in some basic DSR, so we don't end up millions of households using their heat-pumps like a gas boiler, starting up as they get home. Charging their EV and running their appliances in the early evening, with all of this extra demand hitting the evening peak. 

Britain should also be more outward looking, learn from other countries, start considering options like the French approach of having standing charges based on network capacity, and more time of use tariffs, to give households an incentive to use the electricity system efficiently to keep costs down.