In its latest “energy outlook” report, Bloomberg New Energy Finance says wind and solar photovoltaics (PV) will supply almost 50% of global electricity by 2050. Wind, it projects, will produce 26% and solar 22%, with renewables overall supplying 62% of the total. That’s despite electricity demand by 2050 increasing 62%, resulting in global generating capacity almost tripling. Nuclear will then be at 7% and fossil at 31%, according to this outlook, so renewables will clearly have won — although emissions from the fossil sector will still rise.
IRENA, the International Renewable Energy Agency, is more optimistic. In a new report it says renewables and energy efficiency, boosted by electrification, could provide 90% of the necessary reductions in energy-related carbon emissions to limit the global rise in temperature to well below 2°C by 2050. Renewables can supply 86% of global power, and with electrification, they would provide 75% of the emission reductions needed. It sees electrification as a vital part of all this, especially since it can help balance variable renewables: “Clean electricity will be the principal source of power, combined with ‘smart’ digital technologies that make it possible to take full advantage of the growing amounts of low-cost renewable power”.
Electrification ahead
“In a highly digitalized future with strong global climate policies, electrification of energy services will be pervasive,” says IRENA. “Electric or fuel cell vehicles would largely replace fossil-fuelled cars and trucks, and heat pumps and electric boilers would substitute for oil and gas furnaces in buildings and industry. Electricity from renewables could also be used to make hydrogen, synthetic gas or liquids for applications where direct electrification is difficult.”
The IRENA report looks at how this mostly variable input can be managed, with case studies from front runners China and Germany and also Italy, examining how grid balancing has been achieved. IRENA says flexibility is the key and “emerging innovations are not only further increasing flexibility on the supply side but are now also widening the availability of flexibility to all segments of the power system, including grids and the demand side”.
Greening gas is not so easy
However, there is still a way to go. It is not just about shortfalls, for example. All too often the only option when there is too much power is curtailment — dumping it. That’s a big issue in China. But China is dealing with it, with strategies such as improved grids: curtailment levels at wind farms dropped to 7% in 2018 from 13% the year before, while at solar PV plants curtailment dropped to 3% from 5.8% over the same timescale. In terms of meeting peak loads, China has, less appealingly, retrofitted old coal plants to reduce minimum load levels. This, IRENA says, “turned out to be the most feasible approach to add flexibility in the short-term due to lower lead-times and lower costs compared to investing in open-cycle gas turbines or pumped storage”. Germany has mostly done something similar, while it waits for the (delayed) upgrade of its grid system. But what’s also needed there and elsewhere is full smart-grid demand-management and more storage, including of “Power to Gas”-derived hydrogen (P2G). IRENA looks to smart digital technologies, which it says “promise greater system flexibility, permitting maximum use of low-cost renewable power, including for transport”, along with new applications such as charging of electric vehicles and renewable-based production of hydrogen. But it also mentions frequency/voltage support systems, as provided by Italy’s synchronous condensers, used in Sardinia.
Not just electricity?
The emphasis on electrification, and balancing via power grid-linked systems, is understandable. In IRENA’s vision, there will be a lot of green power available, much of it variable, and some of the balancing options are electricity based — supergrid power imports and exports, for example. But not all of them are. Apart from batteries, in which electricity creates chemical charge for short-term storage, and pumped storage, using power to create potential energy by pumping water uphill to a hydro reservoir, most longer-term storage systems rely on converting electricity to more easily stored heat or gas. It could be that heat and/or green hydrogen storage will become significant options for balancing — hydrogen via huge underground cavern stores and heat via giant hot water or hot rock stores. Some pilot projects are underway for heat storage, for example in Germany, looking ultimately to GWh-scale systems, and also for hydrogen, with a P2G-linked underground storage system in the UK.
What’s the outlook for bioenergy with carbon capture and storage?
What’s more, we are not necessarily limited to using renewable electricity for the input energy. Solar heat can have significant potential. Geothermal and biomass heat likewise. This heat can be sourced and used direct, locally. But, if need be, heat can be transmitted some distance from source to user or storage facility, without major losses. The district heating network in Prague, for example, is supplied with heat from a waste-to-energy plant 65 km away. That said, if we want to transmit energy longer distances, then gas, in pipes, makes more sense, using biogas in addition to P2G hydrogen. There can be the issue of gas leakages, as I discussed in an earlier post, and Berkeley in California recently even banned the use of gas in new buildings. But that’s all about fossil methane (and shale gas), not hydrogen or green gas. It would be unfortunate if the green gas piping/use option was blocked in the US – P2G conversion is just picking up there.
Hydrogen or biomass?
Green gas transmission might be superior to power grid transmission in some situations, and green gas can help with balancing, but will there be enough green gas — biogas and synthetic hydrogen — to transmit and then use? The World Energy Council (WEC) recently surveyed views on hydrogen, including P2G “green hydrogen” and synfuel P2X derivatives, and is quite hopeful. The Council sees hydrogen production expanding significantly and says that “hydrogen producers using electrolysis all mentioned technology maturity and falling costs as recent key developments. Combined with imports, the economic fundamentals of P2X may be about to change”. So the organization reckons hydrogen and derivatives, produced using renewable sources, may well have a bright future in some sectors. WEC sees around 47% of these sources being used for transport by 2040, 18% for balancing, about 13% each for power and heating and 9% for industry. Hydrogen is also seen as a key new option in a new IEA report, and featured heavily in the recent G20 summit in Japan, which is pushing hydrogen strongly. “The cost of producing hydrogen from renewable electricity could fall 30% by 2030 as a result of declining costs of renewables and the scaling up of hydrogen production,” says the IEA. A new report from Stanford University is also optimistic about hydrogen economics.
By contrast, although the potential biomass resource is very large, there are environmental constraints on biomass as an energy source, most obviously land-use conflicts. The use of wastes apart, biomass is a land-, and water-, hungry option. Biomass use faces impact issues in nearly all sectors, for example with the use of forestry-derived wood for power production and growing biofuels in vast palm oil plantations for vehicle fuel. What’s more, the value of biomass as an energy source is fundamentally limited by the very low efficiency of plant photosynthesis. As Stanford’s Mark Jacobson says, wind, water and (direct) solar power technologies use much less land and represent far better choices for power production, the only exception being the use of waste.
However, for heat production matters may not be so clear. Biomass, and biogas, are storable, a big advantage for the inevitably variable-demand heating sector. And the use of biomass/biogas as a storable fuel for back-up/peaking plants and for Combined Heat and Power (CHP) plants, linked to large heat stores, offers a valuable, flexible balancing option. With CHP, the ratio of heat to power output can be varied to match varying heat and power demand and varying green power supply. That may give biomass an edge.
Some optimists think that, despite the problems, biomass can also do well in many other applications — and should be pushed hard. Fatih Birol, IEA executive director, believes biomass is a vital part of the mix. “Modern bioenergy is the overlooked giant of the renewable energy field,” he says. “Its share in the world’s total renewables consumption is about 50% today, in other words as much as hydro, wind, solar and all other renewables combined.” And the IEA says that biomass will continue to lead growth in renewable energy consumption to 2023, due to its rising use in the heating and transport sectors. We shall see. But the UK’s Renewable Energy Association says that bioenergy is currently the largest UK renewable: supplying 7.4% of primary energy, 11% of electricity, 4% of heat, 2% of vehicle fuel. The association insists that expansion is vital to meet climate targets and looks to bioenergy supplying 15% of UK heat, power and transport energy by 2032. Some environmentalists won’t agree.
