Downloads, Technical Calculator and Other Information.
Input one variable
Energy
Quantity
5556 kWh per tonne
Dry hardwood Firedwood Tonne
9.5kWh per m3
Natural Gas m3
4000 kWh per tonne
Dry Wood Chips tonne
7 kWh per Litre
LPG Litres
10.3kWh per Litre
Heating Oil
4900 kWh per tonne
Wood Pellets Tonne
3.956 kWh per litre
Waste oil Litree
8.95 kWh per litre
Diesel litres
KWh
BTUH
Megajoules
Water
Input two variables
LPM(liter per minute)
GPM(Gallons)
Temp Drop C
Temp Drop F
KWh
Btuh
Pressure
Input one variable
Bar
1 Bar * 14.50
PSI
1 Bar * 100
Kpa
1 Bar * 10.2
Head meters
1 Bar * 33.46
Head Ft
Temperature
Input one variable
Celsius
Fahrenheit
Distance
Input one variable
Meters
Feet
Inches
Area
Input one variable
Meter Squared
Feet Squared
Yard Sqaured
Gas usage $
Input two variables
Annual gas cost $
Winter Gas cost $
(Less) Summer cost $
Cost per MJ
Total kWh for winter heating
OR
Gas Usage MJ
Input two variables
Annual gas usage MJ
Winter Usage MJ
(Less) Summer Usage MJ
Cost per MJ
Total kWh for Winter heating
Boiler Efficiency
Heat Pump equivalent running costs
Cost per kWh
Actual heat generated kWh
kWh consumed HP using COP 4.5
Estimated running costs
Solar PV installed
If Solar PV is installed, this could significantly increase savings
Savings $
Savings %
Canberra | 35 17 S 149 08 E | 550m - 650m |
Cooma: | 36°12'S 149°08'E | 800m - 850m |
Bungendore:
|
35°16'S 149°27'E | 700m |
Braidwood: |
35°27'S 149°49'E | 660m |
Bega: | 36°41'S 149°51'E | 50m - 100m |
Glycol is useful in freeze prevention and for corrosion protection, but as well as being expensive, it has some nasty properties too. Read this article on glycol and its use in hydronic heating.
The Apricus website has a method for determining the efficiency of a set of tubes, but of more interest is the overall system efficiency. The system efficiency is what really matters - how much of the heat that lands on the roof can be collected and stored in the tank? In this very interesting article on evaluating the effficiency of evacuated tubes in Canada, the author measures everything necessary to do exactly that, and finds that the result is approximately 40%. Bear in mind that the location he is talking about is East Coast Canada - 46N which is 10 degrees closer to the pole than we are in Canberra. The weather is a lot more favourable here.
Water should enter the slab at 40 and leave at 30, so adjust the flow rates on the blue parts of the manifold accordingly. The flow rate needs to be between 2 to 3 litres / min. The higher the flow rate, the less time the water spends in the pipes, so the heat transfer is less.
Use a pipe size to and flow rate to get a fluid velocity of 1.2 to 1.8 m/s. Above the minimum flow velocity of 0.6m/s ( or 2ft/sec) water returning from the collectors will entrain bubbles and carry them back to the tank. More than 1.2m/s ( or 4ft/sec ) will cause noise in the line not to mention being inefficient.
For the solar loop, a good rule of thumb is 1 GPM for a set of 30 tubes, or 3.8 litres per
minute.
At this flow rate, 3 sets of 30 tubes needs 3/4" pipe or otherwise the water velocity will
be too high.
Dr Ben in
his article Determining
the Proper Flow Rate for Solar Hot Water Systems recommmends
0.025 GPM/ft2 or 1 litre per minute per m2. For 6 30-tube panels each with an absorber
area of 2.4m2, thats 14 litres per minute ( or 0.23 litres per sec). A variable speed pump
is ideal - slower
in the mornings and afternoons, faster at midday.
Internal diameters for generic PEX pipe taken from "Modern Hydronic Heating"
Thermal Mass Properties (Source: http://www.yourhome.gov.au/passive-design/thermal-mass)
MATERIAL |
THERMAL MASS (volumetric heat capacity, KJ/m³.k) |
---|---|
Water | 4186 |
Concrete | 2060 |
Sandstone | 1800 |
Compressed earth blocks | 1740 |
Rammed earth | 1673 |
FC sheet (compressed) | 1530 |
Brick | 1360 |
Earth wall (adobe) | 1300 |
AAC | 550 |
Watch this: Drainback systems compared to glycol
Pipe runs must be sloped at least 21mm per metre for effective draining.
If the vertical distance between the tank and the collector is more than about 4 or 5 metres, you may be in trouble. This is because the water will turn into vapour at the highest point( ie at the outlet of the collector, whick will break the syphon effect) To do your own calcs, look at this spreadsheet drainback system calculations You need to know the elevation of your location - you can check by going to Google Earth. Canberra ranges from 550 to about 660
http://solarelectricityhandbook.com/solar-irradiance.html
On average, a horizontal geothermal ground-loop system requires about 200m of trenching for every 10kW of compressor load. A typical system would therefore have 3 or 4 loops of piping each 200m long