Archive for the ‘solar’ Tag

Switching the brain channel for solar.   Leave a comment

I’ve been doing a lot of thinking about making my house solar powered.  I see two problems with it, but neither are really technological problems.  They are mental problems on the part of the end user.

This the Cansolair 240.  It has a heat output approximately equivalent to a 1200 to 2400W electric heating element, or 10,000 BTUs.  It’s actually a pretty good thermal solar panel, one of the best.  The first mental problem you have to get over is the ratio of size to energy output.  My toaster and the 240 both produce about 1200W of heat.  The panel is nearly 4 feet wide and 8 feet long.  It has volume of about 15 cubic feet.  The toaster can be held in one hand and has a volume of less than a 1/6 a cubic foot.  I don’t feel like running the numbers, but I suspect, all things considered, that the panel actually takes up less space if you tally everything.  The panel is an energy producer.  For a fair comparison the toaster needs to have added it’s individual share of the the hundreds of miles of power line, the tens of thousands of cubic feet of coal mine, transportation system, and power plant.  (If I was feeling up to it, I could average those things out and get a number, but meh.)  The point is here, you are not used to seeing your share of the entire power production and consumption apparatus  combined and attached to your wall or roof, so it seems disproportionately large.

The other issue is winter heat.  A problem with heating a house with solar energy is that when you need the most (winter) you have the least available and when you need the least (summer) you have the most available.  Winter in the midwest sometimes passes days without sun, and if you are going to go 100% solar, you need a huge thermal mass, and correspondingly huge collection area to make up for it.  The house, in essence, becomes an inhabited box behind the solar thermal collector, which in turn dictates virtually every aspect of the house’s shape and size.  This is particularly a problem if you are being environmentally responsible and rehabilitating an old house instead of building a new one.  The technological solution to this is to separate the house from the collector, and make the collector a fence like object in the backyard.  However, there is a simpler mental solution: drop the requirement for 100%.  The law of diminishing returns kicks in at different points in different locations.  Accept 100% when the sun shines, 0% when it doesn’t, and cover the gap with the responsible use of the lowest foot print technology you can.

100% renewable is almost a religious fanaticism. People use huge amounts of non renable resources to get that last 15% or so. Just slow down, relax, and be content with very good instead of best.

Ice Box ice usage   Leave a comment

So remember how I mentioned that I want to use a small solar powered freezer?  Specifically, this is the freezer I want:

The Sundanzer 50L Why a freezer?  Because if you have a freezer you have ice, and if you have ice, you can refrigerate.  Thus, a freezer grants you both the ability to freeze and the ability to refrigerate. A straight refrigerator grants you only the ability to refrigerate. Why choose one or the other?  Because you have to use a chest type, for efficiency. Chest type reefers are more efficient for a variety of reasons, but the biggest is that they don’t dump all their cold air out every time you open the door. In fact, you can strongly reduce your power usage by just turning a Chest type into a refrigerator by putting a refrigerator thermostat in it.  But the point here is that no one makes dual compartment chest types.  The freezer and reefer unit have to be separate,  so if you can only get one, get the freezer.  Why the Sundanzer 50L?

The Sundanzer because it has 4″ of high quality insulation and uses the same premium compresser that all high end, high efficiency units use.  The 50L because it is the smallest, lower power using one they have.  It only uses about 100W  a day.  That’s the same energy requirement of using a microwave for about 6 minutes, or two bags of popcorn.  That’s why you can use solar power for them.  The idea hear is make a real, old fashioned icebox (only with premium 4″ insulation), and us that as a refrigerator while using the SunDanzer to make ice for it.  How much ice?

Today’s handy fact: Ice use in a well designed icebox is around 1 lb of ice per cubic foot per day.

A 50 quart cooler (The Model T of coolers) has a capacity of 1.671 cubic feet, you’d expect it to use 1.671 pounds of ice a day. Premium stock coolers are listed as staying cool for 5-7 days. That’s 8.3 to 11.7 lbs of ice which takes up 16.6-23.4 quarts. which is approximately 1/3 to 1/2 of capacity…perfectly in line with manufacturer recommendations, and confirming the 1 lb per cubic foot per day.

Finally, the first electric refrigerator for the middle class, the GE Monitor Top was 5-7 cubic feet. GE chose that size because it was a close approximation of the average icebox of the late 1920’s. Going with the above formula, the average icebox should have used between 5-7 lbs of ice a day. Ice came in 25 or 50 lb blocks, so you would need around two 25 lb blocks a week or one 50 lb block. Which if I recall, is reasonable reports of people who remember using iceboxes.  How big is a 25 lb block of ice? 10″x10″x7″ is the standard.