[Greenbuilding] South-facing windows are net energy gains...

[jfstraube]

I dont know if a tank in a single house is a good solution.  There are major benefits in increasing the number of houses connected to the tank above 1 but these smooth out when more than around ten (just remembering the plots of energy draw vs number of house).  A major deal is that the heat loss from the tank obviously varies with the surface area of the tank.  But the tank surface area varies with D^2, and the volume varies with D^3.  Thus when you double the tank diameter, D, the area increases by factor 4, and the volume by factor 8.  For many houses, the volume is large, but the area through which heat is lost is proportionaly much smaller than for a small tank.  
Thus, large tanks loose heat slowly and cost less per volume of water stored, and many houses (like 10-100) make for large tanks.  Obviously, if we could make R100 insulation layers for modest cost, the impact of tank size would be less significant (think vaccuum panels, something people are trying to figure out how to do cheaply).
I have seen houses in Europe with exterior 10 000 gallon tanks (that should do it for an efficienct house!) and I have seen 2000 gallon tanks inside houses in Fairbanks Alaska (which may not be enough, even though the house is designed aiming for PassivHaus, in Fairbanks HDD14000!!!).  
Somewhere in that range is likely the answer for a modest good house aiming for high solar heating fractions.

On 2011-01-12, at 12:09 PM, Sacie Lambertson wrote:

> Thanks John, possible to use a central tank and find such savings in a single house?  How large a tank are we talking about?  S
> 
> On Wed, Jan 12, 2011 at 11:03 AM, John Straube <jfstraube at gmail.com> wrote:
> I have friends who worked on this.  The houses are all R2000.  It would have been more economical to insulate better.. and just using the central tank, no ground loop, would generate most of the savings with far less cost.
> The overall system is very expensive.
> Check under publications for the newsletters
> 
> _______________________________________________
> Greenbuilding mailing list
> to Send a Message to the list, use the email address
> Greenbuilding at bioenergylists.org
> 
> to UNSUBSCRIBE or Change your List Settings use the web page
> http://lists.bioenergylists.org/mailman/listinfo/greenbuilding_lists.bioenergylists.org

John Straube
www.BuildingScience.com



-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.bioenergylists.org/pipermail/greenbuilding_lists.bioenergylists.org/attachments/20110112/105dfe70/attachment.html>