How To Create A Solar Sand Battery Heater | Free Heat This Winter!

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Sand batteries are not a new concept but can be an impressive way to collect extra solar power during the day to heat your home day or night! I will walk through the setup I used to heat a small room and we will take temperature readings through the day and into the night to see the results and how effective a cheap sand battery could be as an emergency heat source.

DISCLAIMER: This video and description contain affiliate links, which means that if you click on one of the product links, I’ll receive a small commission.

[everydaysolar]

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DISCLAIMER: This video and description contain affiliate links, which means that if you click on one of the product links, I’ll receive a small commission.

[charanvantijn]

Nice concept, but a couple of remarks... -1- With the fan, a thermistor is a temperature dependent resistor. You meant to say a Peltier element/thermo-electric element. -2- Connecting solar panels directly to a resistor (heating element) does not use the panels at their best. You would need an MPPT controller. -3- The round cooktop element is rated for higher temperatures, which is what you need. The long water heater elements are made to heat water. At the much higher temperatures that you're using them now, they will not last long. -4- You're doing this experiment with lots of sunlight plus you didn't show the ambient outside temperature. So how would this work in winter with a lot less sunlight and below freezing temps? Please keep up these experiments, I;m curious how this scales up.

[PeterSedesse]

You are kinda recreating the pathway already done. What you are ultimately going to reach is that the optimal way to do this is to insulate the sand box, which allows the temperatures to get much higher and be almost permanent, and then run water pipes through the sand that feeds out and heats a radiator. There is a company in Norway that has a sand battery the size of farm silo, which then distributes hot water to hundreds of homes for heating... in winter, in Norway...

[TheKingOfInappropriateComments]

My cats would love that. It's a litter box and it's made of warm.

[koskos]

The main thing missing is temperatures in the room! Also some graphs with temp over time will be nice (both room temp and sand temp.).

[user]

This might be nice for a mini greenhouse outside in winter

[dellmerlin]

To get the most power from the solar panels match the resistance of the panels to the resistance of the heating element. David Poz has an excellent video and spreadsheet to do this. To continue the keep it simple concept, use a kitchen oven, connect direct to PV, keep voltage around 100v and bypass switches/thermostat for safety, leave door open, fill with bricks. When sun shines it heats room and bricks. At night hot bricks heat the room.

[johnkay]

Excellent video presentation. I currently use my 4.6 kwp of solar pv to power my house via a standard grid-tied inverter. Then heat-up my old fashioned storage radiators through an Immersun unit, so that the rads / kettle / shower heater; only use just surplus electricity from the panels, rather than exporting such to the external grid. The old fashioned storage radiators in the UK are just basically heating elements inside a brick pile, with insulation around & then encased in a metal skin. A simple bi-metal thermostat limits the maximum temperature.
This has worked so well for me since 2011 that my electricity bill is only about £40 pa. So I'm well pleased.
However, in the potential event of SHTF, if the electricity grid goes down, then your direct routing of the DC from the panels would still be of considerable use. A simple sand battery is a great concept.
Thank you for the video.

[robbehr]

Nice video! Many solar systems have extra capacity that is throttled by solar chargers. I wonder if a water heater could be powered by directing extra productivity to the heater. In wind powered systems, there is usually a "dump load, " which solar doesn't need. But, what if a solar electric system were designed to use a water heater as a dump load.

[basilbrushbooshieboosh]

Love it.
Getting 10 hours of heating would be the golden point for me.
I'm guessing greater sand mass would be the key for slower heat release.

[soluschristus]

I can offer anyone my experience to add to the best outcome here. I hated a kettle of water on the stove last year to see if it works sufficiently keep the place comfortable. I then tried this same battery model. The sand did not collect the heat as efficiently as water. Also, the water out out steam in the air to humidify my living space. What a noticeable element of indoor comfort! That humidity adds to your sense of warmth, just like it adds to your misery in a cold damp environment.
All the wood structures in the house appreciated it too. I hope this helps someone out!

[SmartLumens]

When you introduce these topics, it's helpful to remind new viewers how to experiment safely around voltages over 50V and power levels over 100W. (fuses, protecting wires from physical damage, etc) It can't hurt to repeat a safety message on each video.

[Cholla]

WAY cool, er or, HOT! Just realized this might be the right concept if you encapsulated your floor foundation of a 12’x12’ “Tiny” house which I am a builder of, with sand. It might take a couple of days to get the temp right or you could end up cooked! Thanks Scott for the awesome tutorial!

[LFTRnow]

When doing the math, keep in mind that the resistance of the elements go up with temperature. The power rating is typically AT the temperature it is to be run at. The stove element gets far hotter than the water heater element (since the water heater elements are supposed to be in water). In the old days, you could measure the resistance of an incandescent bulb, then power it up and measure the current at its rated voltage - the resistance when on and hot, was at least triple its cold resistance and took under a second or so to reach.

[kirkdoray]

Ecofan in sand, cool (haha). My thought right away seeing you have about 800 watts of panels, is that you should be seeing more like 700+ watts out vs 137w to the stove element and 250w to the water heater elements. Putting the water heating elements in parallel would be a simple and hotter config. Figures:

Panel config - "max power resistance":
One panel: Vmp 34, Imp 11.62, "Rmp" 2.92 ohms
Two series: Vmp 68, Imp 11.62, "Rmp" 5.84 ohms
Two parallel: Vmp 34, Imp 23.24, "Rmp" 1.46 ohms

Resistor-heater element config:
One *stove element - R= 38 ohms
Two in series - R= 76 ohms
Two in parallel - R= 19 ohms
One *water heater element - R=10.8 ohms
Two series - 21.6 ohms
Two parallel - 5.4 ohms 

So I'd try two panels in series (5.84 ohms "Rmp") with 2 water heater elements in parallel (5.4 ohms R).

Since the element resistances were taken cold, they might change significantly (up) as observed in other comments. Of the resistance elements on hand, 2 water heater elements is the closest match

[drzandlcp]

In hvac applications traditionally, resistive loads are wired parallel while control circuits or switches are wired in series if you had your heating elements wired in parallel, you would have less resistance, and therefore be able to dump more amps into your sand with less voltage drop assuming your panels can handle the amp draw

[nevpnevp]

I use a solar air heater which is about 4 ft x 4 ft and during winter when the outside daytime temperature is typically 25°F, the heater will deliver air at ~ 110°F for 6 hours during a sunny day. I prefer this because the only electrical component is a fan which is powered by a 25 watt solar panel. The solar air heater does not block a window - - it is leaning against the outside wall of the house. Of course, when the sun sets, that's the end of the warm air.

[av-ilbf]

Great Content...Great Idea...Forget all the Smarty McSmart Pants comments this concept is an awesome off grid solution for green houses, well houses, people houses etc etc...Bravo!!

[EtudianteAviendah]

Awesome! Thank you for this build and for showing the math calculations. Now I can keep my cat warm in the garden shed without paying $250/mo for grid electric. Also appreciate the links to solar resources for larger projects. Keep up the good work!

[alphawolfsquadrin]

My small 4'x8' DIY greenhouse thanks you for this idea and video. I have a small greenhouse heater that is plugged into more extension cords after extension cords than I'm proud to admit, especially as a firefighter 😬😬. But this is a great idea that I am gonna replace that with ASAP