Battery Storage Project Doesn't Live Up to Hype

A new 200MW battery storage project in Co. Offaly has been hyped up in the media as a project that will "boost use of renewable energy and reduce dependence on fossil fuel-fired power plants."

From the Independent :

BESS (Battery Energy Storage Solutions) involves the storage of power from the grid which is then resupplied on demand. It will allow renewable energy generated at night to be stored, which would otherwise have to be curtailed due to a lack of demand.

The power can then be released back into the grid, avoiding the use of conventional oil or gas-fired power stations to generate electricity.

The 200MW proposed by Lumcloon could provide power for the equivalent of 170,000 homes.

In reality, the storage facility will not generate any electricity. It will not provide power for any home nor will it reduce dependence on fossil fuel power stations. In fact, it will increase dependence on fossil fuels during periods of low wind. 

According to the planning application, the main purpose of the storage unit is to provide a quick injection of power to restore balance to the grid when there is a fall in system frequency. A fall in system frequency could occur when there is too much wind generation in the system and not enough conventional. According to the Lumcloon Energy website, the facility will need to respond within 5 seconds.

The storage unit is an appliance, like a washing machine, in that it will be a consumer of electricity. It could be called on at any time to inject power, so it will need to be fully charged at all times. So while it will be able to charge at night when there is surplus wind energy, it will also need to charge during periods of low wind thereby increasing dependence on fossil fuel. Therefore, it will be useful during periods of high wind, but a drain on the grid when there is no wind.  

Ireland's only pumped storage facility, Turlough Hill, is also a net consumer of electricity. It has a fixed regime, where it stores electricity at night when it is cheap to do so and exports electricity during the day when prices are higher. Lumcloon is similar but different. Turlough Hill trades in the single market like any other generator. Lumcloon, on the other hand will be paid for providing "system services".

These services must be provided to the grid when requested by the grid operator at short notice , unlike electricity which is bid into the market in a competitive pricing system in advance. They are high quality sophisticated high voltage and frequency services.

A grid run on low levels of renewable energy and supplied mostly by conventional generation plant [i.e coal , gas, hydro, nuclear etc] , does not need to provide such services as they are embedded in the product conventional generators provide.

The storage unit will not sell electricity back to the system ( and receive a price for this product the same as an hydro or wind plant would ) , instead it will receive special remuneration set by the regulator and this remuneration is an additional cost to the system and will have to be recovered from the consumer. 

So the net result from this project will be additional costs to the consumer and it will have little impact (or even none) on the reduction of fossil fuels. A long way from the hype in the media.

Storing The Wind

Would storing wind power sort out the intermittency problem ?

One of the solutions offered for wind intermittency is storage. Let's take the recent calm spell, which was interspersed with very high winds, to see if storing wind would balance out the variances and lead to a more stable predictable electricity supply.

Let's remind ourselves of what the recent wind output looked like (Figure 1) :

Figure 1: Raw wind power which is what we have at present

We can see from the 23rd to 30th September, there was some very high wind output, and again at 4th till 7th October. This was interspersed with a very calm spell lasting a couple of days. After the 4th, there was a long period of poor winds lasting about 12 days.

So what would happen if we balanced out this wind variation to provide more stable constant output ?

Assumptions

There are a number of storage options - pumped storage, battery or compressed air. For this study, I assume a 500MW storage device is built and 1MW of stored power produces 1MW output when needed at all times. As far as I know, only pumped storage can provide this type of reliable storage. My understanding is that a battery produces less output when it's stored power is running low than it does at full charge i.e. the 1MW you put in does not produce 1MW 20 days later.

The other assumption made is that once wind power goes above 500MW, the surplus power is stored. When wind goes below 500MW, the storage device makes up the difference to bring output back to 500MW. Only wind power is stored.


Results

In a perfect world, this would result in a constant wind plus storage output of 500MW. However, as you can see below (Figure 2), there is a blip in the storage output at around 3 days in on the 25th September. But output really hits a brick wall on the 1st October, at 9 days in.

Figure 2: Output from a storage unit powered solely from wind

At this point, there is a sudden drop in power from 500MW to 335MW and then to 11MW that lasts a full day as stored power runs out. Then we get reliable output for the next four days but the battery runs out again on the 6th October (two weeks in) and we are once again at the mercy of the wind. At one point it reaches 5MW. This lull in wind and storage power lasts for 12 days.

On the 18th we get good winds again and the battery begins re-charging but the problem is you can't use this power when it was most needed i.e. a couple of weeks prior. 

Figure 3 shows the contribution of the wind plus storage unit towards demand. The storage unit actually comprises 2,500MW of wind and 500MW storage, so 3,000MW in total. For 3,000MW of capacity, as you can see, you only get very small amounts of power out - about one seventh or 15% of peak demand - when the unit is running at full output i.e. 500MW. This compares very badly with gas powered stations (or indeed coal, biomass or any dispatchable plant) which could power 85% of peak demand for the same amounts of capacity.

Figure 3: Contribution from the storage unit towards demand

To add further insult to injury, you still get unreliable and intermittent amounts of power for large portions of the month - 43% of the time in this scenario. So we are back to square 1. 

Conclusions

Storage doesn't work. There are simply too many calm days to make it a reliable worthwhile solution. It's no wonder the Spirit of Ireland proposal, now dropped, intended to use grid power to move water uphill, rather than raw wind power.

Is storage a solution to wind intermittency ?

How much wind energy could be stored last week ? Well, as can be seen above very little.  But still we are frequently told that wind energy could be stored and that would be the answer to all our problems.

So the future still lies with fossil fuels or we might actually get real and at least look at nuclear like the French and English have done rather than building a nuclear plant in a panic in 2030 without proper planning and risk assessments.