Wind, storage and back-up system designer

Wind, storage and back-up system designer



Peak demand, wind and back-up power / energy usage and storage capacity calculator

For the specification and design of renewable energy electricity generation systems which successfully smooth intermittent wind generation to serve customer demand, 24 hours a day, 7 days a week and 52 weeks a year.

Adopting the recommendation derived from scientific computer modelling that the energy storage capacity be about 5 hours times the wind power capacity, the tables offer rows of previously successful modelled system configurations - row A, a configuration with no back-up power and rows B to G offering alternative ratios of wind power to back-up power. Columns consist of adjustable power and energy values in proportion to fixed multiplier factors.

Replies, comments and questions about using the Wind, storage and back-up system designer at this link please.

renewablejohn said:

But who would it be useful to. If I was using wind but wanted a 24/7 guaranteed supply then just have a gas generator of similar size and a gas tank holding 15 days supply. Oh I forgot thats what the National Grid do.

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You could do that but about 70% of your power would come from gas though because wind turbines only supply on average about 30% of their rated power capacity.

If you want a higher percentage of your power from wind (and solar) then you are going to need a different set up, which is where my designer can help.

pappuller said:

We run a 200 cow dairy milking with 3 robots, we are on a 200 amp single phase supply and have usage of approx 100000 kw/yr we have a 10kw solar array and we're wondering if we could utilise any more renewables to generate more of our own electric, we were told that a 10kw system was the max permitted on single phase.

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I'm happy to advise where I can but be aware that I am a scientist with expertise with computers, maths, physics and applied energy science but I don't have any practical experience of building real off-grid systems myself.

The most useful of my tables to assess the requirements for a business is the Off-grid Daily Usage Focus Table - (even if you are on the grid and using grid for back-up power, the calculations are the same).

100000 kWh/year tells me an average daily usage of about 275 kWh but not what your maximum daily usage is?

So I will just pick "300 kWh" as an example maximum daily usage to run the numbers.

This link creates my Off-grid Daily Usage Focus Table for 300 kWh maximum daily usage.

http://scottish.scienceontheweb.net/Wind power storage back-up calculator.htm?usage=300&units=kw#off

I've captured the image of the table and uploaded it to insert here



The entry level system I would recommend is Row G.

In this case, for 300 kWh maximum daily usage, I'd recommend 20kW wind power.

Your "10kW of solar power" if that is the nameplate capacity is not worth 10kW of wind, not in the UK where capacity factors are about 10% for solar, 1/3 of that for wind, less in the winter. It would be different if this was Australia or Arizona but it's not. Sorry about that.

So your 10kW of solar is worth maybe 3kW of wind but in the UK solar is always better mixed with wind power for winter power.

So for a Row G configuration you be looking at at least 17kW of wind turbines at least and I don't know what size they come in but if the choice is 15kW or 20kW then you need the 20kW.

That's the good news. The bad news is that you need 101 kWh of energy storage.

Batteries would work and you can buy a 100kWh battery but it would be very expensive.

If you've got a steep hill and a water supply you could build a farm-scale pumped-storage hydro scheme which should be cheaper and last longer too.

Even then you will still need up to 11 kW (EDITED) of back-up power from the grid which you would use to keep the energy store topped up.

(The other row configurations need less back-up power but require more investment in generators and storage.)

Then you'd need a contractor to put it all together and automate it and keep the grid manager happy.

Scottish Scientist said:

need up to 11 kWh of back-up power from the grid

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Strange. It is not allowing me to edit my post now.

All those wind powers should be in kW not "kWh." Well it is late.
Well I got them edited eventually but it keeps telling me that it can't be edited.

pappuller said:

we are on a 200 amp single phase supply

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Scottish Scientist said:

That's the good news. The bad news is that you need 101 kWh of energy storage.

Batteries would work and you can buy a 100kWh battery but it would be very expensive.

If you've got a steep hill and a water supply you could build a farm-scale pumped-storage hydro scheme which should be cheaper and last longer too.

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Oh and your energy store needs to be able to regenerate at your peak power whatever that is.

You say you have a 200 amp supply and that might be capable of 200 A x 230 V = 46kW. How much of that peak power you need I have no idea?

Whatever, remember your peak power requirements when you are buying your battery or your turbine generator for the pumped-hydro scheme.

renewablejohn said:

Rated power is a nonsense just look at the 900 kw turbines downrated to 400 kw. Also the bigger turbines are now in excess of 40% with favourable sites in excess of 60%.

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The modelling I did assumes an actual maximum annual wind power of "20kW" or whatever and a 30% capacity factor.

So if wind turbine capacity factor was really as good as 60%, which is amazing , and the site was good for wind and was able to generate the turbine's full nameplate capacity at times then, yes, you could cut my wind power numbers in half - so a 10kW wind turbine with 60% capacity factor = 20kW with 30% capacity factor.

renewablejohn said:

With hydraulic turbines they will run 24/7 with the right size accumulators.

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Really? The technology is moving so fast these days. It's hard for an old applied scientist to keep up.

Now renamed as the “Wind, solar, storage and back-up system designer” to mark solar’s debut.
http://scottish.scienceontheweb.net/Wind power storage back-up calculator.htm

I’ve re-programed my (formerly wind-only) grid systems designer to include solar power and I’ve added a few other useful features too.

If readers have any questions, problems etc arising with the new version then please reply to this comment.