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The question of how we store energy produced from intermittent renewables such as solar has always been an issue in the utility market. Until now, that question has not been particularly urgent, as the number and size of solar installations was not large enough. But now, with a critical mass of solar and wind installations around the world, the question of storage has become critical.

There are several options pumped hydro, where water is pumped up to a higher elevation for later use; solar thermal; compressed air energy storage (CAES); electrochemical batteries; and hydrogen. (For more on pumped hydro and solar thermal storage, see Utility-Scale Energy Storage.)

The hydrogen advantage

While hydrogen may not be the most efficient of the four options (see table), it does have many advantages over the other technologies that mean it could be a suitable solution for utility-scale storage of energy from renewables.

Energy storage options. Source: IFEU-Institut fur Energie und Umwellt for schung Heidelberg GmbH., and Frost & Sullivan
Energy storage options. Source: IFEU-Institut fur Energie und Umwellt for schung Heidelberg GmbH., and Frost & Sullivan

The investment costs and amount of land required for pumped hydro and CAES are very high, explains Suba Arunkumar, author of a Frost and Sullivan market report. And batteries cannot cope with the large amount of energy storage required for large-scale energy storage applications. Hydrogen has the potential to be an online power source with automatic control that can respond rapidly to correct fluctuations, with a response time of less than a minute.

The hydrogen market has been growing over recent years with an increasing number of pilot plants in the US and Europe, yet many challenges still lie ahead before the technology can reach commercial scale (see diagram). There are currently not enough companies involved in the market, says Arunkumar. The industry needs more R&D effort invested in developing safe storage technologies for hydrogen and, while there are lots of electrolyser manufacturers, the industry needs more large-scale fuel cell manufacturers to invest.

Hydrogen Energy Storage Drivers and Restraints

While Arunkumar believes there will not be an overall winner in the energy storage race, she points out that hydrogen can be used for many more applications than simply for utility-scale storage and this may fuel its future growth.

Once hydrogen has been obtained by electrolysis from water, it does not have to be turned back into electricity using a fuel cell. Hydrogen is so much more than just a route to electricity it can be used as a fuel to generate heat, like natural gas (it holds nearly four times more energy per mass than natural gas); it can be used as a chemical to make fertilizer and many other compounds; and it can be used in fuel-cell cars.

Diversity drives the market

It is this diversity of applications for hydrogen that has driven the market and makes hydrogen an attractive way of storing energy.

But for utility-scale applications, electrolysers must be scaled up to the MW range, and this is a major challenge admits Manfred Waidhas, business development manager at Siemens hydrogen solutions business subsegment. We currently have several 100kW demonstrators and we believe we will be ready in time for when demand on the grid will grow. For photovoltaic systems, the MW range will be sufficient. While electrolyser manufacturers like Siemens do not tackle the downstream issue of what to do with the hydrogen once it has been produced, or how to store it, Waidhas is keen to point out that storing hydrogen underground has proven effective. Hydrogen has been stored underground in Teeside, UK, for decades without significant leakage, says Waidhas. In fact the self-discharge is orders of magnitude lower than that of any battery!

Siemens has several 100kW electrolyser demonstrators and hopes to have MW systems ready soon
Siemens has several 100kW electrolyser demonstrators and hopes to have MW systems ready soon

One solution to the storage problem is not to store hydrogen at all, but rather move it on to where it is needed. We already have a huge storage and transport system that is all bought and paid for and can be used for hydrogen, says Daryl Wilson, CEO of Hydrogenics. It is the natural gas pipeline system. Hydrogenics is pioneering what it calls power-to-gas the idea of feeding excess electrical power as hydrogen into the natural gas grid. The company recently announced a deal with Enbridge, owner of the worlds largest liquid pipeline and a company that also has significant investments in photovoltaics, to jointly develop utility-scale energy storage in North America.

Wilson admits that power-to-gas is just one of the many ways in which hydrogen can be used. We live in a world where energy has traditionally been separated into different industries we use gasoline for transport, natural gas for fuel and electricity for power. Hydrogen has the potential to be used for all these applications and so brings a new economic flexibility, says Wilson. Of all the energy storage solutions available, hydrogen is the only one that will be able to cope with demand. If Germany continues of its path of implementing renewable energy, it may need to store up to a months worth of energy. You cant do that with batteries!

Pulling it together

Today we are in the somewhat ridiculous situation where we are giving handouts to windfarms to not input electricity into the grid because we have not invested in the storage solutions to cope with this extra supply.

Kris Hyde, technology manager at UK company ITM Power, agrees. For small-scale applications (Whrs), batteries make sense, but for MWhrs of energy, hydrogen is the answer, he said. ITM Electrolysers have no moving parts and can theoretically run for years without maintenance, so they are ideal for remote and industrial applications. As more renewables come on-stream, the ability to manage the grid becomes a greater challenge. Today we are in the somewhat ridiculous situation where we are giving handouts to windfarms to not input electricity into the grid because we have not invested in the storage solutions to cope with this extra supply. In order to make hydrogen commercially viable we need to solve storage issues, increase efficiencies and scale up electrolysers. We need a lot of people to start pulling together in the same direction.

Written by Nadya Anscombe, Contributing Editor, UK, Solar Novus Today

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