Cooking the Christmas Turkey with Wind Energy

The following graph shows the Wind Energy profile and Demand for the past month for the island of Ireland :

1)  The black line is the maximum available wind output, i.e. wind capacity. This is about 3,000MW for the island of Ireland.

2) The two circles show periods when wind energy was increasing during periods of decreasing night time demand. This wind energy ends up being shutdown or curtailed.

The graph shows the trouble in relying too much on wind energy during the Christmas season. In short, the turkey is unlikely to get cooked. Maybe there will be a chance if families wait up all night, although chances are there won't be much wind then either. Most days, as you can see, the wind output falls far short of the potential wind energy available. 

I would like to wish all the readers a Very Happy Christmas and hope you get your turkey cooked despite the crazy energy policy !

Irish Wind Output Lows of 2015

Reblogged from CAWT blog

As 2015 begins to fade into the memory the media will be full of lists of the “highs and lows” from the year.  Last year our report of the Irish wind output lows for 2014 was one of the most read posts on our blog so here are the lows for 2015 (ROI).

As with last year our print media only seem capable of reporting on wind output highs – no doubt the data is churned out of the Irish Wind Energy Association (IWEA) PR department, see for example Stormy Week Sees Wind Energy Hit Record Generation (PDF).  In order to provide a little balance set out below is a table of the lowest wind output recorded, for the Republic of Ireland, in each of the last twelve months.  The lowest recorded being periods in August, September and October when wind output was at a sustained level of just 1MW (all figures were sourced from EirGrid information webpage).

Month	Output Low	Date & Time
January	16MW	22/01/2015 01:30
February	5MW	10/02/2015 07:00
March	3MW	18/03/2015 03:45
April	5MW	07/04/2015 09:30
May	14MW	07/05/2015 07:30
June	6MW	23/06/2015 09:00
July	3MW	01/07/2015 10:00
August	1MW	18/08/2015 09:30
September	1MW	07/09/2015 07:45
October	1MW	03/10/2015 15:30
November	11MW	04/11/2015 04:45
December	20MW	26/12/2015 10:30

For some context for readers in relation to the output figures, according to IWEA the island of Ireland has 233 wind farms (199 in ROI) with an installed capacity of 3,042MW (2,400 in ROI).   Demand on the island of Ireland fluctuates between 2,600MW – 6,100MW but reached a high of 6,878MW in December 2010.  It is clear therefore that wind energy outputs of between 1MW – 20MW (ROI) represent a very poor return for the Republic’s 2,400MW installed capacity.

So, the next time you read an IWEA inspired “record Irish wind output” story check back to this page and visit EirGrid’s information page to confirm that despite the spin, the energy produced by wind turbines is unpredictable, intermittent and totally dependent on the backup of conventional fossil fuelled power plants such as those fuelled by gas, oil, coal or peat.

Wind Energy is NOT the same as Conventional Energy

A response to American Wind Association Blog :

Wall Street data: successful PTC cuts wind’s costs, job not done

It is a commonly held belief that wind energy is the same as energy from other sources. But this is not the case. Take this article for example :

Say you deposit $20 in the ATM near your office. A short time later, you withdraw it from the ATM near your house. You now have a different bill than the one you deposited, but that’s irrelevant; you still have $20. 

This aspect of the banking system is analogous to how the electric power system works: it aggregates all sources of electricity supply and demand over a large geographic area, allowing one to add wind energy in one area and use an equivalent amount of electricity somewhere else on the grid. 

Just as it would be impossible and pointless to insist that the $20 bill you withdrew in the banking example be the same one you had deposited earlier, it would be impossible and pointless to require an electricity user to specify the exact power plant they receive energy from.

Wind energy is not dispatchable. Conventional power stations provide dispatchable power. You can dispatch up a power station when there is extra demand for electricity. You cannot dispatch up a wind farm. You can dispatch down a wind farm but this is obviously not as useful as dispatching up. For this reason, you cannot build a grid around wind energy, but you can do with conventional generation. So 1MW generated by conventional sources is many times more useful than the 1MW generated from wind sources (In addition, the 1MW from the former provides synchronous power crucial to the stable running of the grid).

So to use the above example, you deposit 20 Lira and then later you take out $20. No country in the world could or would allow such transactions to take place. But this is exactly what happens with wind energy.

The integrated nature of the grid allows companies who wish to use wind energy to add it where it is most cost-effective to do so, even if the location of their primary demand center is in an area that is less suitable for wind generation. Many large companies are now using this strategy to increase the percentage of clean energy on the grid, adding supply in one area and using an equivalent amount of electricity in another. Purchasing wind energy in this way allows these companies to meet their sustainability goals while saving money.

The wind energy provided by a company may be of little use to the grid. Most of its power may occur when demand is low. The result is an over-supply of power when what is required is supply that can match demand and effectively replace older supply. Wind energy can never do that and it's capacity credit diminishes with each MW added.

So it may make these companies and their customers feel happy but actually there is little benefit added. Fast acting plant must be built to back up wind once capacity reaches high levels thereby negating any benefits due to the wind.

Another myth is perpetuated in the same article :

American wind power opponents also claim that because wind is a variable resource, it can’t generate electricity at 100 percent of capacity. But the truth is that no energy source runs at 100 percent capacity 24/7, 365 days a year; and wind’s percentage is actually comparable to the average hydroelectric or natural gas-fired power plant’s output factor.

Powering a data center on a single fossil or nuclear plant would not work either, because those plants experience unexpected shutdowns or maintenance outages about 10 percent of the time (and often cannot or do not run flat-out the rest of the time). Nuclear and most fossil plants also cannot easily change their output in response to changing electricity demand, so they alone couldn’t meet the facility’s needs for this reason as well. In almost all cases a data center or factory is a poor place to build a power plant of any type, whether it be fossil, nuclear, or wind, as most sites lack the fuel source and other services needed for operation.

First of all, data centres do build power generation units onsite. Indeed, the Apple centre in Galway will have large reserves of diesel generators which can quickly switch on in the event of loss of power.

The writer mistakes intermittency with outages. A power station requires back up in the event of an outage. Outages occur between 10 and 15% of the time. Somewhat ironically, outages occur more often in a system with large amounts of intermittent energy, like wind, due to the increased cycling that generators are forced to do with wind on the system. Hence, the need for more fast acting, but inefficient generators to act as back up.

Wind energy is intermittent but can also suffer from outages. A recent problem that occurs in larger turbines is that of axial cracking in bearings which has not been solved. There are other technical problems, particularly with larger turbines. When these break down, that's an outage, the same as when a power station breaks down. But a wind turbine's fuel source is intermittent, hence it's output varies with the weather. This means when a turbine is fully functioning, it still can't be depended on to cook the turkey. This is not a problem for conventional generators unless there is a fuel shortage, which is not a problem for the foreseeable future.

And no, storage does not solve this problem !

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.