Renewable power generation is currently let down by its intermittant nature - but solving the storage problem could transform the market

Barny Evans

At the moment the fatal flaw in idealistic visions of a world being powered by renewable energy is that most of the sources are intermittent, and do not give a guarantee of when they will produce. They can only function because there is a national grid and network of power stations to provide power when the wind doesn’t blow and the sun doesn’t shine.

Until now renewable energy has acted like a teenager ashamed and annoyed with their old, unfashionable fossil-fuel parents, but still refusing to move out, because they can’t stand on their own two feet. There are exceptions, but they still have very significant limitations, as does nuclear.

The answer is to store the power when it is produced ready for when it is needed. However, power storage is incredibly expensive, necessarily inefficient, and our entire system of power supply has been designed to avoid the need.

We do have small amounts of power storage in the form of hydro and a few others, but in general our system is designed to ramp supply up and down in response to demand.

Grid level storage is being explored with methods including pumped hydro, chemical batteries, compressed air, conversion to hydrogen, and there are grid storage projections in 2050 from 7-60GW. I am not sure anyone has a clear advantage, but the investment and rate of progress in the sector is enormous.

In particular, batteries are improving rapidly (driven by other issues such as electric cars, laptops, phones) as much as grid power. When there is that much focus of capital and brains the rate of development can be incredible. Think of computing power or photovoltaic (PV) prices.

There are many potential side effects and unanswered questions. The grid itself would become less efficient as there would be fewer users to spread the costs.

Let’s assume we solve the challenge of storage for a moment. Although the obvious uses will be for stabilising the grid, what if we had individual power storage on a business or domestic scale? If you have a ~4kWp, photovoltaic system on your house, as many do, it will probably generate about as much power as you will use in the home in a year (~3,200kWh). The problem is it will generate when you don’t need it; during the day and even more in the summer.

Discussion of price parity between PVs and fossil-fuel is meaningless at present, yet this will change if power storage becomes affordable. If people and businesses can genuinely use the power of their system and disconnect from the grid the implications are enormous. Most people and businesses won’t be able to do this but even if 10% or 15% did the disruption would be incredible. It could mean that owners of homes with large roofs or businesses installing a combined heat and power (CHP) or wind turbine could become independent.

There are many potential side effects and unanswered questions: people who didn’t own their home or can’t use simple renewables may feel they are trapped on the grid. The grid itself would become less efficient as there would be fewer users to spread the costs.

So is it a libertarian dream where another need for central control disappears, along with 3D printers and the Internet? Will governments become the only investors in long-term projects as no commercial organisation will take the risk of an investment becoming stranded as technology change accelerates?

We are a long way from that point, with costs needing to reduce significantly. Grid/local storage remains tiny, but when that change happens it could be a rapid transformation.

Barny Evans is principal consultant, renenwables and energy efficiency, at WSP