Wednesday, 22 April 2020

Is thermal storage a serious potential contributor to electricity supply flattening?

In managing electricity demand, we are normally concerned with avoiding peak demand, in order to reduce strain on total capacity.
But with intermittent renewables, we also have a potential excess supply problem, when output from wind and solar is high, and demand is low.
Large industrial users are good at taking advantage of such situations, but the domestic sector, where peaky demand is now most prevalent, is not.
In Canada, the electricity supply companies are known to supply large water heaters to domestic consumers. The suppliers control when electricity is used to heat these stores.
Would it be worth doing the same in UK?

  • Heat generally has a lower value than electricity per kWh - except in times of potential overgeneration.
  •  Creating solar and wind capacity at a level to minimise gas generation rather than to fit within existing capacity constraints would mean long periods of oversupply, requiring storage, supply constraint,or dumping
  • ESCO's are now looking at thermal storage as a way to manage renewables, particularly in SME's.
Can it happen at scale before we have a substantially strengthened grid?

Wednesday, 8 April 2020

Is it more environmentally friendly to use electricity when the grid is showing low average carbon emissions?

The National Grid in UK has a very useful app that tells us what the carbon emissions per unit generated are. Clearly this will be at its lowest at times of high wind or solar generation, and relatively low gas generation.
The implication is that  it is better to use electricity when the average is low.
But is that actually so?
Unless we are in danger of shutting down wind or solar generation for lack of demand, which almost never happens in UK at the moment, each additional unit used comes from the supply that is responding to demand, which is currently almost always gas in UK.
Every unit of solar or wind electricty generated is always used. Switching something on at times of high renewable generation makes no difference!
So, when is the best time to use electricity?
The focus should continue to be on flattening the demand for gas, which will make gas generation more efficient, and ultimately reduce the capacity requirement for gas generation.
If you want to be sophisticated about it, track the gas power station output, for example from Kate Morley's excellent site   
Otherwise, the best thing to do is to avoid the winter peak from around 3-8pm, and try to shift non-time-sensitive consumption from the day into the night-time trough from around midnight to 6am.

Tuesday, 4 September 2018

Low Carbon Technologies set to make Peak Demand Worse!

According to BEIS (which includes what was DECC) without demand side response (DSR) we will increase peak domestic electricity demand from  24 to 31 GW, an increase of 7GW or 29% by 2030.
Note that the trough is the same, so the curve shape has got worse.
I note they are only allocating a peak of 1GW to electric vehicles, which at 3kW per vehicle is only 330,000 vehicles, or 1% of the present vehicle population.
Most of the peak increase will come, they say, from heat pumps. Storage of heat is relatively easy and cheap, all you need is a larger hot water tank. These are common in biomass heating systems.
How do we publicise the vital necessity for domestic load shifting, awareness of which needs to accelerate now to meet future demands?
At the moment it's just word of mouth, so keep on telling people about it!

Tuesday, 14 August 2018

Is the Heat Wave over?

Here's a heat wave worth looking at!
Air conditioning uses over 30% of the peak electricity on a hot day in California - and by time-shifting the cooling using stored ice, in some buildings the peak can be completely ironed out.
What's more, the air conditioning capacity needed is reduced, as it's working for longer to produce the same amount of cooling.
As air conditioning becomes more prevalent in UK and Europe, this is becoming an increasingly relevant way to avoid peaks in summer.
Conversely, in winter, if we are to use electricity for heating, it will become worthwhile to store hot water or even steam to reduce peak consumption.

Tuesday, 31 July 2018

Could Solar PV Power the World?

This map from data supplied by the International Energy Agency (IEA) and interpreted by Land Art Generator shows the area required to provide all the electricity needed in the world from solar PV.

One flaw- they suggest that Europe could be supplied from the Sahara desert - but as we know, peak consumption in Europe occurs after dark, and the sun has set even in the sunny Sahara at that time.

All is not lost however - the deserts of USA are still sunny at peak times of European consumption, so all we need is a link from the USA to Europe - see my blog on an Arctic Circle supergrid.

If you don't like the idea of linking the world up like this, then you and the rest of us are going to have to shift a whole lot of consumption out of the after dark peak. Have you told your friends yet?
When I suggest this, people often say storage is the answer - which at the moment is much more costly than nuclear.

So I say  Reassess, Reduce, Reschedule!

Monday, 25 June 2018

It's Hot in Arizona!

Salt River Project, or SRP as it is now more commonly known, is an innovative electricity supplier in Arizona USA. They have a wide range of demand-related tariffs, including a time-of-use tariff which has at its most extreme, a factor of three difference between peak and off-peak costs per kWh in July and August.
This highlights the value and in this case the relative ease of substantial time-shifting of air-conditioning. Environmentally conscious Arizonans have a number of options:
  • Build houses with high thermal mass as well as high insulation, so that cooling can be done outside of peak times, and advantage can be taken of the large differences between day and night temperatures in desert areas.
  • Use storage aircon to build up ice as a store of coolness before peak times.
  • Start cooling the house well before peak times and tolerate some increase in temperature during the peak.
  • Use PV to generate electricity for cooling 
Coincidentally, Arizona is where PV can best be generated to meet UK's winter peak, as their solar midday occurs during our evening peak. So the PV they use during their summer could supply our electricity in winter.

If you want to avoid the cost of a Northern hemisphere supergrid to allow this, then shift your time of use and get others to do the same!

Monday, 21 May 2018

Centrica - British Gas - and Combined Heat and Power

Centrica (British Gas to most of us) is going on the offensive with CHP.
It makes sense:

  • Their business is selling gas
  • The most efficient way to use gas is to produce both heat and electricity
  • New gas-fired power stations are decreasingly attractive to them because of the lower load factors in the present energy mix
Do we want gas CHP? It still produces carbon. But how else are we to heat our homes?
Heat is the biggest challenge to reducing carbon in UK - perhaps the best is the enemy of the good, and we should embrace CHP at least for the moment.