From: Bob Vennerbeck <vbob-AT-whipplestreet.net>
Date: 06 Mar 2010 11:19:02 UTC   (06:19:02 AM in author's locale)
To: xtensionlist-AT-shed.com

Wonderful thread on solar heating !!

Ard -

You already have the English terminology - 'heating degree days' and 'cooling degree days' are calculated in the USA on the difference between the day's average temperature and 65°F

Since your baseline temperature of 17°C is slightly lower than 65°F (I get 65 F = 18.3 C) it makes me wonder if the baseline varies from country to country, climate to climate, or culture to culture...

I've always assumed the notion of 'zero degree days' was the point at which you did not NEED any heat (or cooling).

Vbob

On Mar 6, 2010, at 1:29 AM, ard jonker wrote:

>> This particular thread has been fascinating. Reading about all >> these projects
>> has definitely piqued my interest in attempting to install some >> kind of DIY
>> solar water heater this spring/summer.
>
> Ah, we've got at least one switcher. I might keep quiet from now on, > my goal has been reached ;-)
>
>> If you decide to comment further on this topic, could you provide >> your
>> approximate latitude? Here in Michigan I live at 42.6°N and I'd be
>> particularly interested in knowing what kind of results other folks >> in
>> similar latitudes are getting.
>
> Rather than having the latitude only, I think it is also important > to mention climate (land, sea) and a number what we call > 'graaddagen' (degree days) in Dutch, which is the annual sum of > (17°C-X°C), where X°C is the average circadian temperature in > Celcius. That number is linearly related to the amount of energy > needed for heating a house. Possibly a similar relation (X°C-17°C) > can be made for warmer climates, where Air Conditioners are used.
>
>>> From reading some of the entries though, it seems that many of you >>> live
>> much further to the south than I do, so I'm wondering if it would >> be realistic
>> to expect the same kinds of results as some of you get.
>
> lat 52.4N,lon 4.9E will that do? 2400 graaddagen, 18°C summer > average, 10°C annual average. Bottom composition and average > temperature (at 100 yards) will also be of importance and have to be > specified for good comparison.
>
> We have a soggy bottom (no pun intended) of 12°C year round. That > means with a 100 meter closed ground loop (32 mm ø hose going down > to 100 m and up again) you can draw 10 kW @12°C. Of course, the > energy well has to be replenished in summer (looping groundloop > water through the hydronic heating floor and walls, dumping of > excess solar heat) and dry soil needs deeper loops.
> High-lattitude low-yield can be countered partly by putting the > collector perpendicular to winter sun, to have a more constant > energy harvesting year-round, rather than maximising total > production per year as one would do with electric panels.
>
> A scatterplot of 'graaddagen' (anyone knowing the proper term in > English, please?) of each day against heating energy (kWh or m3 gas) > consumed, you can easily determine this parameter for your house and > see how more insulation and more heatpipes/collectors improve > performance energy-wise.
>
> 10°CPF 12°CSF 18°CdF 1m=3.2 ft
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