Monday, March 10, 2014

Going solar.

If you spend a fortune on 50KW of solar panels and the batteries to store 3 days worth of power, you can live just like you always have, with no changes needed.  But this is foolish, expensive, and wasteful. A better way to go solar is to adjust your life to require a much lower level of power, and size the solar panels to meet that reduced footprint.  This means that you need less batteries, less panels, less wiring, and less things to go wrong.

Of course, this would require people to take positive action, so it would be bad and difficult to get anyone to agree to do.  A better way would be to let the appliances work together intelligently in order to reduce the maximum power draw, and to run the most power hungry appliances during times when the batteries are charged and you can run entirely off the solar panels.

Power efficient appliances.

There are freezers and refrigerators that are much more efficient and lower power than anything you can buy at a mall store.  These freezers and refridgerators are smaller than the huge ones in most people's houses today, but you have to ask yourself, do we really need such huge fridges?  Can't we make do with less rather than eventually having to make do with none.  There are washing machines that use much less energy and water to run as well.

One of the things you have to watch out for are hidden energy costs.  A 1200 Watt microwave oven actually draws 2400 watts of power.  Many gas ovens use up to 400 Watts of power when the oven is on to keep the ignitor hot enough to light the gas as it kicks on and off.  A watt meter like the Kill-A-Watt meter is very useful to see how many watts and KWh a machine uses.

Solar Water Heating.

One of the highest energy expenses in any home is the water heater and heating water on the stove. One thing that helps with this is to use a small, well insulated water heater that can provide several cups of boiling water on demand. This small water heater could keep running even when the house was in a degraded mode, allowing people to make hot beverages and small hot meals.

By directly heating water with the heat of the sun you can reach amazingly high efficiencies.  Any system I build will have a large insulated water tank to store heat to both heat the house and my own drinking water, and a solar panel designed to heat antifreeze up to 180 degrees.  Or there may be a water tank to store heat for the house and a different tank for drinking water. This heated fluid would circulate in heat transfer loops around the base of the water tank to transfer the hot water to the cold water in the bottom of each water tank.  Another loop could come from a wood stove to heat the water in the tank as well.  The best design is to limit the length of your water lines and heavily insulate both lines.  More loops could be placed in the floor to heat the floors in your house, the most efficient kind of heating.

Solar cooking.

It is possible to cook entire tasty, nutritious and healthy meals in a couple of hours times in solar ovens. You can also sterilize water this way for drinking.  There are entire websites devoted to these techniques. It would be interesting to explore how to build several solar ovens into the design of a house to allow free cooking of foods.

Home entertainment.

My media player is already based on the Raspi running XBMC. This media player only draws 3.5 watts, plays HD video, and it is easy to load in another SD memory card to turn your TV into a game system that can play most of the games written before about 8 years ago.   As similar more powerful boards are released every few years it should be easy to upgrade the player.   I eliminated the older file server I was using, saving 10 watts of power, moving all the functions it was performing over to the Raspi already acting as my media player.  So far it has been working flawlessly.

One of the most power hungry appliances in the house has always been the TV, and while they are more efficient for the screen size than older TVs, a large plasma or LCD monitor can still draw up to hundreds of watts.  I would like to use a low powered projection device drawing no more than a dozen watts with a highly reflective screen  in a dark room to get a great picture while not drawing hundreds of watts of power.

The intelligent house.

Ideally an advanced house would schedule when the various appliances ran.  I would load the laundry and dishwasher, and the house would clean the dishes, then wash the clothes so they were done just as I got home for the day, sending a notice to my phone to put the clothes in the dryer.  While the washing machine motor was running at full speed, the freezer and refrigerator compressors would be turned off for a few minutes.  The water heater would only run when nothing else needed power, turning off when the furnace ran the blower.

In this way, instead of needing to provide 100 amp service, you could run the house on 20 or even 10 amps, if the compressors and motors are made smaller, and more efficient, with a corresponding reduction in the size of the solar array and batteries you need to provide power for a house.  It may be possible to run a generator on demand to top off batteries periodically when there is no grid power available and demand is greater than can be provided by solar alone.

An intelligent house would monitor the environment, in and out of the house, adjust light, humidity, and temperature levels to make things comfortable for the people living inside.  There should be a reporting area that graphs how much power is available projecting how many days the house can provide full power before shifting to a degraded mode of operation.  The generator fuel supply could be intelligently applied to this prediction and usage graphed over time.

It may be possible to run a few LED lights, and run the solar water heater to heat the house indefinitely, while not being able to run various appliances except when the batteries are charged and the solar panels voltage would otherwise be wasted.

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