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Thread: Solar Power Thread

  1. #466
    Super Grandmaster
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    Quote Originally Posted by calypso View Post
    Whats the ROI on such a setup?
    Pretty poor I suspect. But then anyone who goes to this amount of trouble either lives in a rural area with no power or very unreliable power, in which case the ROI is irrelevant; or,

    Is totally committed to becoming self sufficient with regards to hot water.

    In cases like this trying to calculate the ROI just gives you ulcers

    I think it is a really good idea provided the design is correct and efficient.

  2. #467

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    a solar geyser is About R24 000
    depending on family size water usage a average geyser runs 4.6 hours a day. that's 2000 watt geyser running 138 hours a month
    solar geyser with hybrid electrical geyser runs 12 hours a month

    so normal geyser is 138 hours per month at R0.86 p/ kwh is R1.72 per hour R7.91 per day R240.00 per month and R2888.20 per year
    solar hybrid geyser 12 hours per month R0.68 per day R20.93 per month and R251.00 per year
    so a saving of R2637 per year so +- 9 years to paid back. This is normally less because if you go solar geyser you would be energy effiecient with lights appliances etc etc.
    My bill came down from about R1500 to R600 with all we have done which gives me a R10 800 saving a year


    http://energyusecalculator.com/elect...aterheater.htm

  3. #468
    Senior Member
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    Quote Originally Posted by Geoff.D View Post
    Interesting. So what is the sequence? Does cold water first go to the solar heater, from there through the heat pump and finally into the geyser, a in-series installation, or does cold water feed into both the solar panel and the heat pump and then into a common storage tank (geyser?)
    The cold water feeds into the geyser (this is where the inefficiency is!) with both the solar heater and heat pump configured as pump arounds from the geyser depending on the reservoir temperature and time of day.

    During winter when the incoming cold water is at the lowest temperature, it drops the reservoir temperature instead of first begin pre-heated.

  4. #469
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    Quote Originally Posted by calypso View Post
    Whats the ROI on such a setup?
    I installed the system when the Eskom rebate system was still active. I can't recall the installation cost...will have to look in the archives!

    The heat pump has a 1.3 kW compressor with equivalent water heating capacity of 4 kW. Most summer days the water temperature peaks around 65 deg C on average from the solar system. The heat pump only supports when the solar contribution is poor or during high warm water consumption and the reservoir is depleted during night time. During summer my electricity consumption on the heat pump circuit is on average 60 units. IN winter it is more due to the reduced sunlight period and colder water entering the system. I estimate about 100 - 130 units in winter.

    Before I installed the system my geyser circuit averaged 250 units per month in summer time.

  5. #470

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    Quote Originally Posted by maumau View Post
    Just a follow-up.

    We decided against solar. Cost was R130k and it would have saved R3 500pa Even with huge electricity price increases nobody could justify the expense.

    Something that put me off was the battery hums while it discharges. It was going to be installed in a cupboard in the passage or in the garage close to a bedroom. Can't live with that
    You forgetting one massive important factor like the rest ... Electric Vehicle charging off your FREE power. Could you imagine how much Eskom would charge to charge

  6. #471

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    Quote Originally Posted by felixbf View Post
    You forgetting one massive important factor like the rest ... Electric Vehicle charging off your FREE power. Could you imagine how much Eskom would charge to charge
    Well that's if the system has enough solar and battery to absorb the additional load of charging a car (probably out of solar production time)

  7. #472

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    Quote Originally Posted by calypso View Post
    Well that's if the system has enough solar and battery to absorb the additional load of charging a car (probably out of solar production time)
    Don't necessarily need battery storage to charge an electric car.
    Assuming you drive every day in the week, the weekend will charge the car enough for another week /month.

    Panels are the cheapest part of a solar system, never hurts to have more than you need (you size systems for winter use, not summer output).

    Heck, in summer time, system will start charging before work hours anyway. I start getting solar output on my system in summer around 5:45am onwards. Assuming you leave for work at 7:30am, thats a potential few KW top up every morning.
    Eg in my 4KW system, I can usually generate 1-2KW by 6-7am.
    Last edited by lsheed_cn; 07-10-2017 at 05:17 PM.
    http://goingsolar.co.za - My Solar Blog

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