Energy storage: key to renewables

Kari Williamson

Energy storage is well known in off-grid installations, but how can energy storage be used as a way of accessing the grid for connected renewable energy systems?

Energy storage is heralded as a solution to integrate more renewable energy into the grid. Andrew Jones, managing director, S&C Electric Europe Ltd., agrees.

S&C is an employee-owned company headquartered in Chicago, IL, that has been operating in the electricity market for 100 years focusing on connecting electric utilities to the grid. The company customises solutions for customers, including technologies such as voltage control and switchgear.

“We're in the renewable energy market because we actually believe in what we're trying to achieve,” he tells Renewable Energy Focus.

Jones says S&C aims to help utilities maximise the amount of renewables that can be connected to the grid at the same time as helping renewable energy developers get the maximum performance from their technologies.

Furthermore, S&C is not technology-bound: “We work with other people's technology. We're battery technology neutral, and we will work with the best technology [for any given] application.”

He adds: “We are looking at different technologies, the one we do in Australia is a new version of a battery, same as you have in cars, but they've found a way of making the energy density higher, so you don't need as many batteries to get similar storage.”

Voltage control

S&C effectively provides voltage control devices, but this feeds nicely into the energy storage sector:

“We've done a number of wind farms where we've helped them meet grid codes.

“But because wind varies it causes fluctuations in the amount that it can generate, which impacts voltage. If we didn't get involved, the lights would flicker on and off,” Jones explains. He says voltage control helps wind farms that wouldn't normally be allowed on the grid to connect. “This helps community type wind farms connect to the grid at a cheaper amount than they would do normally. We expect to see a lot more of this type of work.”

Community Systems

S&C is currently planning to become involved with community storage projects for renewable energy use. Jones explains that at the moment, when the number of solar photovoltaic (PV) installations (or other renewable energy technologies in a given area) reaches a certain level, the utilities have to come in and “dig up the street to put more cabling in”. The regulators says cabling can only be added in response to known increases, which means that you could have a situation where the same street has to be dug up several times as more systems are being added. “This doesn't seem a very good use of assets or time,” Jones points out.

After our meeting Jones told Renewable Energy Focus that S&C has received an order from the Orkneys (in Scotland) for a community-based scheme.

“We've developed a product that can sit there at the end of a street and take the solar PV when it's there. Most people that will initially buy solar PV will be people that are working, so they are not going to use the electricity. Solar charges during the day, but the peaks are typically when we all come home from work. What this does, is that it allows the solar to feed into the battery during the day, and then when we all come home to cook our teas and put the TV on, it will feed into the houses allowing them to use the renewable energy that's been generated without having to dig roads up and put new cables in.”

The systems would also come in handy as more and more electric vehicles need support from the grid. “It's a bit of a technical quirk; you may use batteries to charge batteries. But it may actually work out to be the most economic way to do it in the short-term,” Jones explains.

Large storage systems tend to be about 80% efficient, but smaller systems can get close to 90% efficiency.

S&C is part of a consortium that will, amongst other things, look at electric vehicle batteries when they have come to the end of their useful lives for this type of application: “We would take control technology and integration, and take end-of-life batteries that have been in the cars but cannot be used in cars anymore, and see if they can provide a useful function on the grid. It may only be at 80% of its capability, but that may be good enough to store solar PV,” he argues.

However, many electric vehicle and battery manufacturers are unwilling to pass on used batteries: they are concerned about liability and would rather just sell new ones, Jones adds.

Larger and Larger

Jones continues that S&C is getting involved in larger and larger projects, despite there being “only three of us doing this in the world at the moment.”

One example where large-scale storage perhaps would have made sense is in the case of the UK in early 2011, when national media reported that the National Grid had to compensate wind farms for unused capacity. Storage systems would limit the need for constraint payments to wind farms, as the wind power would be stored and then used when needed. With a storage price of US$4 million/MW, the cost seems prohibitive, but Jones says: “Even at that price, it's still cheaper than an AA battery.”

“In the U.S.” he says, “we're now involved with 10 projects where we can do this type of thing. They are all connected to grids and they are all helping maximise the use of wind. For example, we're involved in one project which is funded by the Department of Energy called Wind to Battery. They've tried things like storing in batteries, as well as selling the electricity at different times of day when you get more money for it. They've also used it for wind smoothing. I think this site is designed for a capability of 10 MW. By putting the batteries in, I think they were able to consistently put almost 4 MW into the grid. That makes it easier to connect to the grid because you get no variability. It's those types of things that it's starting to be used for.”

Shetland storage project

S&C is involved in a large energy storage project with Scottish and Southern Energy (SSE) in Shetland, involving 6 MWh of storage, which according to Jones allows Shetland to put “more renewables into the grid, and in conjunction with that reduce the reliance on diesel.

“For geographical islands, large-scale storage where people are relying on diesel makes sense. And we expect to see a lot more of this throughout Europe,” Jones says.

The sodium sulphur batteries used for the projects will be 100% recyclable at the end of their life. “The Japanese company we're buying from is in the process of setting up a recycling centre in Germany to deal with this.”

Japan Wind Development, which is S&C's partner on the project, has what could be the world's largest energy storage connected to Rokkasho a wind farm. In Japan, they have a 54 MW wind farm with 34 MW of energy storage, Jones says. “They are in a bit of a unique situation in Japan because of the difference between night and day tariffs, which are quite different. They charge the batteries during the night then they sell into the grid for a guaranteed amount – at certain times during the day. The Japanese utilities wouldn't let any more wind farms connect without knowing they would have a guaranteed supply at any particular time,” he explains. Jones believes this could be applied elsewhere as well.

At the moment, however, it would only pay on geographical islands because of the cost of storage technologies. “That's why people have been lobbying to try to get it recognised that maybe something like a feed-in tariff should apply, because it will then incentivise the market to spend time getting the volumes right for the battery technology.”

Support needed

The UK House of Commons recently recommended in its Electricity Market Reform, that energy storage should get similar incentives to the feed-in tariffs for renewable energy generation. Jones says: “It's recognised that this will enable a bit more renewables in the grid and remove the issue of intermittency. You cannot change the wind, so you've got to find some way of storing it.”

Although it appears decision makers are now becoming increasingly aware of the importance of energy storage, Jones believes more needs to be done if renewable energy targets are to be met within the 2020 time frame.

“There are more people developing wave and tidal devices in the UK than people working on storage technology globally. We all recognise [storage] as essential to getting more wind, and with these high penetration targets in Europe and globally, the need is there, but people are spending more time on wave and tidal,” Jones says.

“To me storage is a way of integrating renewables and helping with demand side management,” he concludes.

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Energy infrastructure  •  Energy storage including Fuel cells  •  Green building  •  Wind power




22 February 2012
Hydrogen Storage-- I do not see any thing about making hydrogen using renewables such as solar-to-hydrogen by photoelectrochemical water splitting then store the hydrogen for 24/7 use in fuel cells to make electricity.. You are missing an important renewable process. Thomas W. Oakes, PhD Solar Hydrogen Energy Co. La Mesa, CA USA pairedhelix@cox.net

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