Friday, 28 July 2017

What does a sustainable energy system for 2050 look like?

The National Grid recently published their annual 'Future Energy Scenarios' report which describes alternative futures for electricity and gas supply and demand to 2050. There are four scenarios of which only one satisfies our carbon commitments but I am struck by how similar they are in terms of electricity generation - where they differ greatly is in gas demand and use of smart technologies to manage infrastructure - including smart meters and time of use pricing.

The four scenarios are:
Steady stateFocussed on security of supply and short term thinking
Consumer PowerRelatively wealthy and market driven
Slow ProgressionFocussed on long term environmental strategy
Two degreesEnvironmental sustainability is top priority

National Grid's report shows developments over time from now until 2050 but in this post I concentrate on the end goal and how Two Degrees achieves our carbon targets while the others fail.

Energy supply - similar across all scenarios
Steady state is not a very interesting scenario, so for brevity I have not shown it in the graphs. Here is 2050 electricity supply. The future scenarios all have more renewables (wind and solar), more nuclear power and very little gas. Two Degrees has the most wind and nuclear and the least gas; what gas it does use is combined with CCS (carbon capture and storage).
Electricity generation in 2050, compared to 2016

The total electricity requirements are not that different either: Consumer Power uses the most but Two Degrees is not that far behind. Slow progression has slower growth overall and finishes up with not much more than current use.

Annual electricity demand TWh/year
Consumer Power422
Two degrees402
Slow Progression365
Current (2016)332

Energy demand differences - switching away from gas for heating
However these similar totals hide big differences in the source of demand. Two Degrees includes a massive switch from gas to electric heat pumps for heating, with some going hybrid (gas boiler supporting a heat pump).

Residential heating fuels in 2015 compared to 2016
Gas demand down from power stations and heating, up from transport
This chart shows the impact of these changes on overall gas use. Demand from power stations is drastically reduced in all scenarios and heating demand is down in Two Degrees as we have seen. The surprising bit is a sharp increase for transport: battery power may or may not be practical for HGVs but National Grid envisage up to a third of the fleet switching away from oil to natural gas, which is cleaner than oil.
Gas demand in 2050 compared to 2016
Peak time demand from electric cars needs smart management
Increasing numbers of electric cars can have a big impact on peak electricity demand which is a concern. Increasing peak demand requires investment to strengthen the grid as well as more generation capacity to meet that demand. Both Consumer Power and Two Degrees have a lot of electric vehicles but in Two Degrees they are better managed, with smart chargers taking most of that load off peak. This chart compares electricity demand for cars across the scenarios, considering both average demand and demand in peak times.

Extra demand due to charging electric vehicles on average and at peak times in 2050
In Consumer Power, 20% of peak demand is for car charging - almost 18GW. But in Two Degrees the peak time demand for charging is only a little more than the average - it could even be less if more drivers take care to charge off peak whenever possible.

Other smarts to keep peak demand.
The overall peak demands are shown in the table below. Consumer Power has the highest, again. Two Degrees keeps the peak down even though there is increased load from electric heating by making more use of smart technology. For example in this scenario smart meters are rolled out quickly and consumers respond to time of use tariffs by shifting demand away from peak times. Many of the homes with heat pumps have thermal storage units (about the size of a hot water tank) so they can adjust the times when they use power.

Peak electricity demand GW
Consumer Power85
Two degrees73
Slow Progression70
Current (2016)61

Distributed generation leads to demand troughs that can damage the network
Peak demand is not the only problem for the transmission and distribution networks - peak supply from small distributed generation is an even bigger headache. Small generators that are attached to the distribution network are not turned off when power demand is low so either we have to increase demand (National Grid calls this service Demand Turn Up) or the big power stations have to be turned down. We have already started to see this effect. For example on a sunny day in March this year gas and coal power stations had to be turned down to offset the increase in solar (see Clean Energy News). You may think this is a good thing and it is, up to a point, but if it is not managed sensibly embedded generation can lead to high voltages and physical damage to the grid. Consumer Power is once again the most difficult scenario, with 50% of capacity connected to the distribution grid and another 18% from nuclear that is not very flexible either.

Distributed storage is one answer
The easiest solution is smart use of battery storage on the network to smooth out both peaks and troughs in demand. This can be either dedicated storage or making use of electric car batteries. Distribution network operators such as UKPN are trying various strategies. They recently announced support for small scale battery storage associated with renewable energy (see UKPN unveils fast track process for small-scale storage, Solar Power Portal) and they are also interested in grid scale battery storage services (UKPN embraces DSO future, Clean Energy News).

We need smart meters to make this work
So there you have it. A plausible sustainable energy system for 2050 requires not just a lot of renewable energy generation but a lot of smarts to manage it effectively. It needs flexible energy storage and smart time of use pricing to manage demand peaks and troughs. People with electric cars can benefit greatly by shifting their use away from peaks - and so can people with heat pumps if they have a thermal store. But first we need the smart meters, which are fundamental to making this work.

[1] Future Energy Scenarios 2017 (National Grid) July 2017

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