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.

The Wind, storage and back-up system designer is hosted separately on the Scottish Scientist website. You must click to open the web-page.

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One thought on “Wind, storage and back-up system designer”

  1. Noting the story in “CLIMATE ACTION. In Partnership with UN Environment”
    CLIMATE ACTION
    In Partnership with UN Environment
    100% renewable energy fuelled micro-grid successfully operated in 24h test in Illinois
    http://www.climateactionprogramme.org/news/100-renewable-energy-fuelled-micro-grid-successfully-operated-in-24h-test-i

    I made the following comments …

    Well what’s needed is a system design that provides power on demand, reliably 24 hours a day, 7 days a week and 52 weeks a year. To achieve that without diesel back-up generators, I would recommend –

    store energy capacity = 1.5 days x peak demand power
    annual maximum wind (+ solar) power = 7 x peak demand power

    (assuming I only know the system’s peak demand power) –

    So for this Ameren micro-grid where I assume “the 50kW onsite microgrid which powers an American research facility” means that the peak demand power is 50kW, I would therefore recommend
    (see Grid Watch Demand Focus Table http://scottish.scienceontheweb.net/Wind%20power%20storage%20back-up%20calculator.htm?peak=50&units=kW#grid )

    storage energy = 1.5 days x 50kW = 36 hours x 50kW = 1800 kWh
    (whereas all the Ameren system has is “500kWh” which is too little by a factor of 3.6)

    annual maximum wind (+ solar) power = 7 x 50kW = 350 kW
    (whereas all the Ameren system has is “250kW” which is too little by a factor of 1.4)

    By “too little” I mean too little for 24/7/52 operation, even though the Ameren system worked perfectly well in the test conditions of that particular 24 hours. Clearly wind and solar power have days of plenty and days of shortage. My recommendations tell you how to design a system that works even on the days of shortage – for those dark days of winter when there’s not much wind blowing either – that’s when your system design gets its ultimate test.

    However, my above recommendation assumes that the system’s average power demand is about 60% (30kW) of peak power – (50kW), with an average daily energy usage of about 24 hours x 30kW = 720kWh and a higher maximum daily energy usage.

    If the average power used is significantly lower than 30kW and in particular if the maximum daily energy usage is significantly lower than 720kWh then it may well be that not so much storage or wind+solar generation is required.

    Supposing although a micro-grid had a peak demand power of 50kW its maximum daily energy usage never was as much as 720kWh but was a lot less.

    Let’s assume that the average power was, say, only about 10kW and their average daily usage only 24 hours x 10kW = 240kWh, but their maximum daily energy usage in any one day was a maximum of 482kWh.

    Then all that would be needed would be
    store energy capacity = 2.4 x maximum daily energy usage
    max wind (+ solar) power = 0.4666 per hour x max daily energy usage

    (See Off-grid daily usage Focus Table http://scottish.scienceontheweb.net/Wind%20power%20storage%20back-up%20calculator.htm?usage=482&units=kW#off )

    energy storage – 2.4 x 482kWh = 1157 kWh and
    annual maximum wind (+solar) power = 0.4666 per hour x 482kWh = 225 kW

    which is still a factor of 2.3 times more energy storage than the Ameren microgrid has (500kWh) but is exactly the wind+solar power they have.

    So it all really depends on what the maximum daily energy usage of the system is. Peak power demand doesn’t completely specify a system’s generation and storage requirements because both peak power and maximum daily energy usage are important design considerations.

    Likewise, a 50kW micro-grid which always runs flat out at 50kW (peak demand power was also the average power) and therefore had a maximum daily energy usage of 24 x 50kW = 1200kWh would have a greater energy storage and generation requirement.
    (See Off-grid daily usage Focus Table http://scottish.scienceontheweb.net/Wind%20power%20storage%20back-up%20calculator.htm?usage=1200&units=kW#off )

    In this case more energy storage 2880 kWh and maximum wind+solar power 560 kW would be required.

    Like

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