Whatever next? New energy technology and systems

The last couple of years has seen some old certainties disappear. Renewable energy has moved from being a marginal, expensive possibility to becoming a cheap wide-scale winner. Offshore wind was once see as the most expensive of the main renewable options, but it is now booming and may soon be one of the cheapest, probably only beaten by solar, with talk of some offshore wind projects leading to negative prices. That has already happened with some onshore wind and also now PV solar projects- which are set to continue to boom globally. With low marginal running costs, and falling capital costs, these renewables can undercut anything else on the grid at times, in generation cost terms.

 

Of course they can’t do that all the time, so there is an extra cost for balancing these variable renewables, especially for meeting peak demand when renewable supply is low. But the daily demand peaks only last a few hours and can be flattened/delayed by smart grid/variable power pricing systems, and new energy storage technologies can help maintain supply during longer lulls. We are in the midst of a flurry of innovation in this area.

 

Storage

 

Batteries are fine for short term storage, helping to cover demand peaks and maintain grid frequency and voltage stability, and they are improving, but for the medium to longer term there are whole host of long duration storage options-  including hydro pumped storage, cryogenic liquid air storage, compressed air storage and underground cavern-stored green gases. The later include hydrogen, made by the electrolysis of water using renewable power, and methane and other syngasses, made from this hydrogen, including ammonia.

 

As I discussed in an earlier post, hydrogen is being talked up as a clean all-purpose gaseous fuel, if produced via green Power to Gas conversion (P2G), synthetic methane gas too, but some people like liquid fuels, such as methanol, since they can be more easily stored and transferred. However, unlike any of these options, Ammonia (NH3) has the virtue of having no carbon atoms. So when it’s burnt there is no CO2 produced.  So some see it as a key way ahead. Though there is also the non-chemical storage option, stored thermal energy, either of heat or of cold, which may be able to play a key role at power to heat system boundaries, or even in heat to power conversion.

 

A lot of possibilities. For the moment, most of the emphasis is on hydrogen in its various guises, including for balancing and heating, but also, more immediately, for use in vehicles. There is plenty of surplus green power at low cost to run electrolysers, and, as the scale of the hydrogen market builds and volume manufacture of electrolysers expands, the P2G route looks likely to be increasingly attractive economically. So it could take over the from the ‘blue hydrogen’ fossil gas conversion/CCS route. Aurora Energy Research says that hydrogen could supply 480 TWh by 2050 – half of UK energy demand. That may be overstating it. National Grid ESO only looks to 190TWh for a limited scale and range of purposes. But P2G is obviously one of the ones to watch, with Proton Exchange Membrane  and Solid Oxide cells fighting it out for dominance. PEMs seem to be winning.

 

Heat Pumps

 

The other one to watch is heat pumps.  There are disagreements, as I have discussed in an earlier post, but some see them as the best route to heating, better than hydrogen, since they are very efficient energy convertors, in some cases able to convert 1 unit of power to 3 or even 4 units of heat.  That puts them in different league to hydrogen based systems, since power-to-gas conversion efficiency is at best 80%, even assuming some co-gen heat recycling. However, using power for heating has its problems. At present, most home heating in the UK in done by gas and the gas grid carries up to 4 times more energy than the power grid- it has to deal with large evening winter peaks.  Switching over to power for heating would probably mean the power grid had to be much enlarged, even given heat pumps’ more efficient use of the power.  Note also that their claimed 3 or 4 times efficiency mark up is not always achieved in practice, especially for air source heat pumps in cold damp climates. Some of the time the energy gains can be minimal.

 

New improved conventional heat pumps might help to achieve more reliable results, but the more radical approach is to combine conventional heat pumps with hydrogen gas fed boilers in a hybrid system which can use the gas to meet demand peaks, so as to avoid power drains on the grid. That is the compromise approach backed by the UK government at present. So we may see some innovative new hybrid systems. Indeed, National Grid ESO says that, in the UK the could be ‘over 8m hybrid heat pumps responding to market signals and shifting demand between hydrogen and electricity systems by 2050.’

 

Less likely, we might see the adoption of a different compromise- gas fired heat pumps. They are less efficient than electric heat pumps, and are not widely used, but running on gas does avoid the power grid drain issue. Larger units are more efficient, but that is also true of electric heat pumps. Though it might then make more sense in some locations, to have large gas-fired Combined Heat and Power (CHP) units feeding community wide district heating network, as well as the power grid, since CHP operation can give even higher overall energy efficiencies and opportunities for balancing via large scale heat stores. So that would be a major energy system change for balanced heat and power management.

 

Integration

 

As can be seen, the innovation path ahead may not just be about individual bits of new hardware but may also involve whole system changes, integrating new devices and new wider smarter systems for flexible management of variable renewable energy.  In addition to local heat networks and heat stores, and smart local grid management to match local variations in power demand and supply, we may also move to a new system in which some power may be imported and exported long-distance using HVDC supergrids to help balance regional and  local variations in supply and demand. See my next post. While some things can and should be done on the small scale local basis, it may thus be a case of all change, with some of the changes also being quite big.