New to solar, have a couple questions

System · December 2011

I eventually want to do complete solar but until then I need to start learning about it.

The first thing I want to do to get into solar is a small project of mine. I am building a pond on the side of my patio which I want to run a 100W heater and about a 100W pump year round for some tropical pond fish. I live in the high desert so water freezes here without heating.

What I want to do is set up one solar panel system to support the heater and the pump. I simply don't know where to start with this, where to shop, what to buy?

Any advise for this 200 watt setup?

BB. · December 2011

Re: New to solar, have a couple questions

If you have an installation (pump+heater) and grid power already, just purchase a kill-a-watt meter or equivalent. Then measure your daily power needs.

With those numbers, a paper design for your system is just plugging in the numbers.

By the way, the kill-a-watt type meters are great for anyone to use around their home and measure existing loads (fridge, computers, entertainment systems, etc.). First step towards conservation is to know your loads. I highly suggest them for people even if they never will go Grid Tied or Off Grid solar.

Spending money on conservation can, often, give you great returns on your investments (spend a $1,000 on a new fridge/freezer now or even computer system, and save $20 per month for the next XX years).

-Bill

Cariboocoot · December 2011

Re: New to solar, have a couple questions

Welcome to the forum.

The thing is, it's not just 200 Watts. It's 200 Watts times however many hours the load will be running for the Watt hours. This is where things get tricky. The pump running 24 hours a day adds up to 2400 Watt hours, which is a lot of power in itself. The heater would be thermostatically controlled, so may or may not be on depending on the temperature, but that adds up to the potential of another 2400 Watt hours. So this "little" project turns out to be twice as much power as I use at my off-grid cabin per day!

Panels only produce power while the sun shines, and for the rest of the time you have to store it in batteries. But the total amount you will use needs to be "harvested" in that brief window of opportunity when the sun does shine (usually about 4 to 5 hours under good conditions).

Full off-grid power comes at a significant cost. $1 per kW hour over the life of the equipment is not unexpected. When compared to utility power, it's really expensive. If you were to go for the full 4.8 kW hour potential here, you'd be spending thousands of dollars in capital outlay just to keep the fish happy.

TnAndy · December 2011

Re: New to solar, have a couple questions

Do what BB said....get yourself a "Kill-a-Watt" meter, plug in that 100w pump, and 100w heater for 10 days. Then divide the KwHr reading accumulated on the meter by 10, giving you the power requirement per day.

You'll probably find out it's in the 2-4kw/hr per day ballpark.......you won't believe what it will cost for an off grid system to supply that much power, that seems so little when you plug into the grid. It will certainly be an eye-opener for you. I'll tell you this up front....a single panel won't even come close.....most likely you're looking at 500 or more watts of panel, and a WHOLE BUNCH of other equipment.

westbranch · December 2011

Re: New to solar, have a couple questions

I think you would be far better off to look into Evacuated Tube Solar hot water heaters with a PV powered pump, turns on when there is sun ( and hot water) and off when dark, no batteries needed.

New to solar, have a couple questions

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