Research hints at storage’s wider role

New research suggests electric vehicles could have a key role in using excess solar while also providing grid services. Pic:

New research suggests electric vehicles could have a key role in using excess solar while also providing grid services. Pic:

By Jason Deign

Research in recent weeks suggests energy storage is being considered for a growing role on the grid as renewable penetration increases.

In the US, for example, an organisation called the Institute for Local Self-Reliance (ILSR) has issued a report called Choosing the Electric Avenue that claims a boom in electric vehicle ownership could help smooth the duck curve.

“Timed charging of electric vehicles means afternoon surges in electricity demand can be smoothed out by steadily increasing demand from electric cars,” said the ILSR.

“Additionally, electric cars can soak up excess energy supply by charging overnight to absorb surplus wind energy.”

The report also notes how electric vehicle batteries could deliver ancillary grid services to maintain voltage and frequency equilibrium in the absence of large thermal plants. 

Requiring new market rules

“Taking advantage of this power will require new market rules,” the ILSR said, “but vehicles with nothing more than a Level 2 charger could provide valuable services to the grid.”

The ILSR is not the first body to point this out.

Earlier this year, for example, Ernesto Ciorra, Enel’s head of innovation and sustainability, told Energy Storage Report that electric vehicles could provide grid stabilisation services without the need for any additional forms of storage.

In any event, the Italian utility is also looking at standalone stationary energy storage deployments, particularly following its acquisition of Demand Energy in January.

Where the ILSR report is significant, however, is in reiterating how smart electric vehicle charging could be used to store excess renewable energy production that currently stresses the grid and must be curtailed.

Electric vehicles smooth renewable supply

The ILSR cites numerous sources, including the National Renewable Energy Laboratory, the Pacific Northwest National Laboratories and the Rocky Mountain Institute, which claim electric vehicles can smooth renewable supply.

Even if growth in electric vehicle battery storage can help grids cope with high renewable energy penetrations on a minute-by-minute or hour-by-hour basis, though, there is still an issue of how to deal with long-term climate effects.

Dr Björn Peters warned in March that the need to cover calm, cloudy spells of up to two weeks at a time may mean it could never be economical to aspire to a 100% renewable energy system backed by current storage technologies.

This week saw the issue of how energy systems could become 100% renewable kicking off in the US, in a spat between Stanford professor Mark Jacobson and a team led by Christopher Clack of Vibrant Clean Energy.

And as previously reported, the conundrum is focusing attention on the development of gigawatt-hour-scale technology alternatives such as compressed air and gravity energy storage. 

Highly conceptual technologies

Many of these technologies are still highly conceptual, though.

As a study from the European Academies Science Advisory Council said last month: “No new storage technologies are expected to be commercially deployed on a large-scale in grid-connected applications before 2030.

“In contrast, non-dedicated storage using power-to-heat and power to gas are less expensive and could be deployed earlier, notably as an alternative to curtailment.”

Using excess renewable energy as the power source for power-to-gas (PtG) or power-to-liquid (PtL) production can yield low-carbon hydrogen or synthetic natural gas, which could potentially be used as fuel for vehicles, heating or power plants.

Last month, the European Association for Storage of Energy (EASE) released a set of recommendations to scale up PtG and PtL production across Europe. 

Storing large amounts of energy seasonally

“It is the only energy storage option available to store large amounts of energy seasonally and provide it on-demand to different sectors and applications,” said the EASE paper.

“Flexible and fast-reacting electrolysers can quickly increase their production in times of surplus electricity. This mitigates curtailment of wind farms and helps avoid grid congestion and stabilise the electric grid.”

It should be noted that it is immensely inefficient to create hydrogen from renewables.

In Sustainable Energy—without the hot air, former UK Department of Energy and Climate Change adviser David MacKay calculated that BMW’s Hydrogen 7 limited-edition car required 220% more energy than its petrol-based brethren.

“I know of no form of land transport whose energy consumption is worse than this hydrogen car,” he said.

Less efficient than fuel-cell technology

In fairness, the hydrogen internal combustion engine in the Hydrogen 7 is much less efficient than the fuel-cell technology being used in later commercial hydrogen-powered vehicles such as the Toyota Mirai.

Even so, hydrogen’s low round-trip efficiency probably means it is unsuited to becoming a mainstream replacement for fossil fuels in transportation.

When it comes to dealing with long-term weather effects, though, it may still have a role.

Bruce Lin, founder and chief engineer at Catalytic Engineering, has proposed that hydrogen could be mixed with natural gas to reduce the latter’s carbon intensity.

Processing hydrogen into methane

An even better option, he said, might to process the hydrogen into methane, which is easier to store.

This lowers the efficiency even further, however, which means the cost of energy inputs must be very low and the value of energy outputs must be very high for the process to be financially viable.

The economics certainly would not work today.

But in a world flooded with increasingly cheap renewables it may make sense to mop up most of solar’s daily excess for vehicle electrification, and put some extra overproduction into PtG to save for a rainy, and windless, day.

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