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Observing the world of renewable energy and sustainable living

Solar Air Heater

Private preparations for a ‘sustainable future’ are progressing satisfactorily:

– Solar panels gave me 1450 kWh in the first year on a household consumption of 1550 kWh; that’s almost full coverage.
– Three seasons of running a vegetable garden, making substantial progress every season. Coming season the full garden will be available, providing 100% of potatoes and vegetables. Additionally a greenhouse will be installed in February after the last tree stubs will have been removed and 100 m2 will be available for gardening, enough for two persons.
– Freezers and generator backup are in place.

Motivation: anticipating a global financial “Big Reset“, as well as creating a pension plan not (entirely) based on paper assets. “Peak oil” is of secondary concern only.

The last item on the prepper todo list is space heating support. For that purpose 10 m x 1.6 m garden fence facing South-West is available. The idea is to construct a huge solar air heater, consisting of a large black plate, covered by double glass, so that during the day, air hotter than 21 C (if any) can be pumped into the living room. At a later stage, air from the collector can serve as input for an electric heat pump for temperatures < 21 C. Ideally the black backside solar radiation absorber will consist of black solar panels to gain extra electricity, to be used for the electric heat pump. In the Summer the glass cover needs to be removed to prevent over-heating of the solar panels. At a later stage a heat storage, like a vessel of 1 m3 filled with pebbles, could be added to the system.

Calculations:
[amazon.com] – Duffie, Solar Engineering of Thermal Processes (the classic)
[builditsolar.com]
[ijsr.net] – Designing and Fabrication of Double Pass Solar Air Heater Integrated with Thermal Storage

Detailed project description in Villingen-Schwenningen in (sunny) SW-Germany, near Freiburg.
[copy-net.de] – Project description
[copy-net.de] – Bilderbuch
[copy-net.de] – Results
[copy-net.de] – “Live” data (2010)

Project summary:
148 m2 living area to be heated.
Pre-solar average yearly energy consumption: 2000L oil and 4000 kWh electricity.
28 m2 solar air heater area, resulting in 44-50% solar share of total required heating energy.
Furthermore, the air from solar can be used as input for an air conditioner, resulting in 58.5% solar share.

villingen-schwenningen-luftkollektor2
The Villingen-Schwenningen project

My own last yearly (pre-solar panels) energy bill (1100 euro):
Natural Gas: 870 m3
Electricity: 1550 kWh

1 m3 natural gas = 9.8 kWh
1 liter oil = 8.6 kWh

So my 870 m3 natural gas translates into 991 liter oil equivalent.

Double glass 100 cm * 160 cm (= 1 solar panel) 4+4 mm costs 50 euro.
Solar panel 100 cm * 160 cm costs 210 euro.
Assume 10 panels + glass cover: 2600 euro base price. Add to that scaffolding, back side isolation, pump, thermometer, etc. Perhaps 5000 euro in total.

Quick comparison:

Location DE NL
Living area [m2] 148 32
Collector area [m2] 28 16
Fossil fuel [liter] 2000 991
Electricity [kWh] 4000 1550
Orientation South South-West
Tilting vertical flexible
Cost [euro] 6000 5000
Solar share [%] 58.5 ?

Orientation: slight disadvantage S vs SW
Tilting: slight advantage, no need for strict vertical placement
Living area: advantage factor 4.6
Collector area: disadvantage factor 0.57

Based on these numbers one would expect that I could achieve (much) more than a 58.5% solar share in my personal space heating requirements.

[To be continued]

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