thermal solar panal power source

[tandemsforus]

I have 200 sq ft of thermal solar collectors heating my basement via pex in my poured basement floor, radiant heat system. The system runs great with a 120 volt a/c pump and solar controller.
EXCEPT
When we have a power outage here in the mountains of NC. Then the collector temps can easily reach boiling temp and above if the pump is not moving fluid. The collectors are ground mounted so a drain back or drain down solar system is not feasible. The pump is 120 volt, .80 amp. The system runs at around 4 gpm., 8-10 ft of head.
Am I able to run the existing pump with dc powered solar collectors and inverter totally off grid. Thus when the sun is out, the inverter runs the controller and pump. I was told I need a battery in the system for it to operate. Or would I be smarter to keep a/c pump and power supply as it is and hook up a dc powered pump to cycle fluid to keep temps under control during a power outage.

[SunEagle]

You can find DC pumps and fans that will work directly wired to solar panels but you have to make sure the panel output voltage and the DC motor are compatible.

That is why using a battery to run a DC load or using a battery feeding an inverter to run an AC load is a better plan.

Also try to understand you may want to have that heating circulation when the sun isn't shining. That would require a battery or generator to run that AC pump.

[peakbagger]

I have a PV powered DC pump and its been running for about 14 years. The panel is direct wired to the pump with no battery. Its a March pump that came with the system. After a couple of years I did install an Art-tec controller (arttecsolar.com) that is powered by the PV panel. It helps out in the morning and afternoon as the PV tends to turn on the pump too quickly before the panels are warm, leading to cooling down the tank. I have the basic one, all it does is looks at the collector temp via an RTD and the storage tank temp and only allows the pump to run when the panel is hotter.

It came with a 20 watt panel that didn't have enough juice. I put in 12 volt 48 watt Siemens panel I had kicking around and its fine.

[PNPmacnab]

Check out pond pumps on youtube. Missouri Wind and Solar ( who I loath) have a demonstration of running a small inverter and pump without a battery. It uses a cheap buck converter to regulated 12V. The only trick is you have to add a little control so when a cloud passes and inverter goes into low voltage shutdown it will reset later. It is what I would be using all the time. Pump doesn't need to run at night or when it is cloudy. It actually might pay for itself in energy costs. I'd use a cheap 280W grid tie panel.