Solar Heater B continued (continued) continued

The second solar heater (B) now is connected to the house too, using a nifty flexible hose. It yields a little cooler air than the first one, 49º versus 53º. Heater B has a bit smaller converter, 4 cm narrower, 96 cm versus 100 cm, so 4% less surface area.

Solar Heater B continued (continued)

Frame for the mosquito netting.

Two sides, the netting 2 cm apart.

17:30, sunny: 44º! (110ºF)

Two heaters now. Yes, those greay pipes will be hidden.

But, as you do, then there's rain.

Solar Heater Capacity

All very well, a solar heating, but what does it yield? 50° hot air is of course nice, but is it significant? A calculation.

The system has a fan that moves 70 m³/hr of air, in principle.

The heat capacity of air is 1,005 kJ / m³ it therefore costs 1005 J of energy to make one kg of air one degree warmer.

1 m³ air weighs 1,225 kg.

The outside temperature is about 15º, while 50º is output, a temperature increase of 35º.

If that happens during one hour, there is 70 m³ air 35º warmer.
That costs 70 m³ * 1,225 kg * 1005 J * 35 = 3016 kJ in one hour.

Watt = J/second, so the capacity is 3016 kJ / 3600 s = 834 Watt

The sun emits around 2.7 kW of energy per m² this thing has a surface area of 2.1 m ², and thus captures 2.1 * 2.7 = 5.67 kW energy.

This means that the yield is about 834 / 5670 * 100 = 15%, which is not very different from the efficiency of electrical solar panels (15 - 20%)!

Is the capacity significant? An electric radiator has a capacity of 800W (low) to 1400W (high), the kitchen has a volume of 140m³
I have materials for three solar heaters, so perhaps a few degrees? I hope that will make the difference. And it's free, that makes quite a difference.

You can view solar heaters as a "remote window". Normally the sun shines through windows, and heats up an interior. However, this house hardly has windows, so we'll use these "remote windows" instead.

You can wonder if the 70 m³ per hour air really is achieved is a good question. Perhaps next time.

Solar Heater B (continued)

 Saw - drill - file - glue - clamp

Solar Heater B

Yesterday started the second solar heater, as I have materials for three. This time I screw aluminium profile and wood in one go. That saves a lot of time drilling precise holes in the aluminium, afterwards. Now I drill holes in the aluminium profiles first, punch a hole in the (soft) wood, and glue and screw all in one go. And ready! (Well..)

The Hot box: 50º +

12:00, bright sunshine: more than 50º! Beyond the end of the scale of our thermometer, around the bend!

The Hot Box BROKEN! (solar heater) 3 // Calefaccion Solar ROTO! 3

The mosquito netting apparently pulls so hard on the frame that one bar broke. Repaired with a new extra bar, and some bolts.

Ok, this needs some improvement, it's just the test setup.

52ºC / 122ºF at the exit of the solar heater!

47ºC / 116ºF hot air into the interior.

The Hot Box (solar heater) 2 // Calefaccion Solar 2

Today, 10:200, full sun, outside air temperature 16ºC / 60ºF. Result: 50ºC / 120ºF. Fifty! Not bad. What? Fantastic!
I removed the thermometer at 50, as it's the end of the scale.

The Hot Box (solar heater) // Calefaccion Solar

This house is nice and cool in summer because of the thick stone walls. Alas, that means that also in winter the house is cool, even when sunny and 20º outside, which is not pleasant. The house hardly has any windows at the sun side, so there is no heat coming in. That can be helped, with a solar heater. There are various types, but in principle it's a (wooden) box with a transparent front, and a black contraption on the inside, the "absorber". Air passed through the absorber heats up, and is led into the house. The transparent front can be glass, or a plastic or polycarbonate material. The idea is to isolate the collector from the cold outside air, to prevent heat loss.

The black absorber can be various types. Some people make a pipe of soda cans, painted black. Others use a sheet of black metal. Air passed behind that sheet heats up. A very efficient type is constructed with two or more layers of mosquito netting. Pass air through and it heats up.

If you're curious have a look at: https://rimstar.org/renewnrg/solar_air_heater_types_diy_homemade.htm en http://stonehavenlife.com/comparing-solar-air-heater-designs-performance/, en http://www.builditsolar.com/Experimental/AirColTesting/Index.htm for various types and an efficiency comparison.

I have chosen the "Screen solar air heater (matrix)", with two layers black mosquito netting. As the transparent material I have asked for a sheet of Makrolon 3000 x 2100 x 6 mm to be sawn in three 1 meter wide sheets, so I can build three individual solar heaters of 2.1 x 1 meters. Makrolon is sheet material for transparent roofs. The box is made of thin triplex (4 mm) and 20 x 20 mm wooden bars and some aluminium profile. Used 3 x 10 mm screws and D3 wood glue. A small fan and a 4 Watt solar pan0el for moving the air through.

Today it's ready for it's first test, at 17:00, so near sunset. Outside temperature: 14º C (50º F). Hot air temperature: 38º C (100º F).

Setting sun, eh! Very curious how it'll be in the full sun tomorrow!

I have not insulated the box, nor sprayed it black. I have material for 3 solar heaters, so I will experiment with insulation and black paint with those.

The box is oiled with Tung wood oil inside and outside. (Inside only once.)