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Solar Power Thread

Geoff.D

Executive Member
Joined
Aug 4, 2005
Messages
7,258
How feasible is it to run a Solar Geyser with an Heat Pump?
Not sure I understand the question. A Geyser is just a tank for storing hot water, which is heated via:

(1) An element.
(2) A solar panel
(3) A heat pump.
Or a combination of all of the above.

What is your plan? To preheat water, then feed it via a heat pump, into the geyser? Or, to use the existing solar geyser but use a heat pump to heat the water instead of a solar panel? Should be possible.
 
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grubsner

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Feb 21, 2005
Messages
364
How feasible is it to run a Solar Geyser in conjunction with an Heat Pump?
I have this setup running for the past 6 years. I use the geyser as storage and run the heat pump only when the solar system cannot heat the water during the day due to overcast conditions. I have disconnected the geyser heating element.

Works without any issues.
 

Geoff.D

Executive Member
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Aug 4, 2005
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7,258
I have this setup running for the past 6 years. I use the geyser as storage and run the heat pump only when the solar system cannot heat the water during the day due to overcast conditions. I have disconnected the geyser heating element.

Works without any issues.
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?)
 

qscwbt

Expert Member
Joined
Feb 24, 2014
Messages
1,251
I also run a hybrid setup, 200 litre solar vacuum tube geyser (no element) feeding a 150 litre geyser that is connected via a geyser buddy to normal element
 

calypso

Senior Member
Joined
Feb 10, 2009
Messages
984
I have this setup running for the past 6 years. I use the geyser as storage and run the heat pump only when the solar system cannot heat the water during the day due to overcast conditions. I have disconnected the geyser heating element.

Works without any issues.
Whats the ROI on such a setup?
 

Geoff.D

Executive Member
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Aug 4, 2005
Messages
7,258
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.
 

qscwbt

Expert Member
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Feb 24, 2014
Messages
1,251
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/electricity_waterheater.htm
 

grubsner

Well-Known Member
Joined
Feb 21, 2005
Messages
364
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.
 

grubsner

Well-Known Member
Joined
Feb 21, 2005
Messages
364
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.
 

felixbf

Active Member
Joined
Jan 9, 2010
Messages
43
Just a follow-up.

We decided against solar. Cost was R130k and it would have saved R3 500pa :crylaugh: :crylaugh: 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 :crylaugh:
 

calypso

Senior Member
Joined
Feb 10, 2009
Messages
984
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 :crylaugh:
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)
 

lsheed_cn

Expert Member
Joined
Sep 14, 2008
Messages
2,565
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.
 
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Joined
Apr 13, 2015
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1
I'm building a new house in Steyn City. It will be about 550sqm. I'm looking to go off grid because I actually cannot stand to pay Eskom one cent. I realise it won't be a good ROI but I don't want to be completely roshamboed just because of my hatred of Eskom.

I've just started exploring this option but it's quite overwhelming as I don't know anything about electricity. But here goes:

What solution would someone recommend for going off grid?

I know that I will have to change the way we use electricity. So wash clothes and use dishwasher during sunny days. Try use as much power during the day and only run TVs, lights at night. Not use energy intensive appliances at the same time.

Family of four but may increase to 7 on weekends with relatives staying over

I'm looking to go for two 200l solar geysers on each side of the house with two water rings.

Got a gas hob electric oven.

I have a dishwasher, washing machine, two tvs, two laptops, microwave, pool pump, A rated Samsung 550l fridge, 116 6w LED lights, wood fireplace Morso, toaster, coffee maker, two garage motors. I'm trying to be comprehensive but can't think of anything else right now.

Any tips on what and how much of each to get would be appreciated!

The final amount would determine if it's a case of whether I hate my wallet or Eskom more!
 

thechamp

Honorary Master
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Feb 26, 2011
Messages
12,808
For a start get an estimate of your power consumption, 6×116= 696W for lights only, you can do better and reduce say may be half of that to 3W per light. Get the wattage rating from every appliance you have and add that to get a total power consumption.

A pure sine wave inverter ( I would go with multiple inverters were I in your shoes not just one massive inverter) maybe one for your electronics and another for you heavier appliances like washing machines.It would probably be more expensive but it makes sense to me, since yours is not a backup but a primary power source. Your inverter capacity will be determined by the power consumption of your appliances, e.g. if your total power is 5000W you will need an inverter rated at more than that.

Batteries- Deep cycle, lead acid- cheaper, AGM and lithium- more expensive , higher quality and tech. The number will be determined by the total current your appliances draws, the higher this is, the more batteries you need, the better the quality and their capacity, the longer will be your runtime. Measured in Ah, the higher the AH, the better.

Solar panels to charge your batteries.

You will need an expert to put all of this into perspective, but since you are busy doing your homework you will know which questions to ask. Getting a solar system for a backup is one thing, it being your primary power source is another.
 
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IzZzy

Executive Member
Joined
Feb 17, 2004
Messages
5,758
Hi all

Does anyone know of any reputable solar PV installers in JHB that could quote on a solar backup or solar as a mains source (with feedback into the grid)?

Many thanks!
 

Arthur

Honorary Master
Joined
Aug 7, 2003
Messages
22,359
[MENTION=6360]IzZzy[/MENTION] After a lot of research I settled on an established and reputable local manufacturer/supplier: MLT Drives, hq in Cape Town but with offices nationwide. They've been in this business for decades, have designed and manufactured their own inverters for African conditions, and know what they're talking about and what they're doing. Not the cheapest, but one of the best. Very satisfied customer.

I have 55 panels in three arrays connected to a 12kVA PowerStar II mains-connected hybrid inverter, exporting to the grid. Web-connected. Running since 2012. Fully cost-recovered. And unaffected by load-shedding.
 
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IzZzy

Executive Member
Joined
Feb 17, 2004
Messages
5,758
[MENTION=6360]IzZzy[/MENTION] After a lot of research I settled on an established and reputable local manufacturer/supplier: MLT Drives, hq in Cape Town but with offices nationwide. They've been in this business for decades, have designed and manufactured their own inverters for African conditions, and know what they're talking about and what they're doing. Not the cheapest, but one of the best. Very satisfied customer.


I have 55 panels in three arrays connected to a 12kVA PowerStar II mains-connected hybrid inverter, exporting to the grid. Running since 2012. Fully cost-recovered. And unaffected by load-shedding.
Fantastic! I really wanted to message you but happy you responded. I’ll contact them to see about a quote!
 
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