Tag Archives: power

Environment, Lifestyle

Residential Solar Power System Upgrade

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Last week we upgraded our solar power system for our home. Since we live off-the-grid in Hawaii, this was a major cause for celebration, which included dancing and lots of toasting well into the evening.

We now have a 48-volt system with 1600 Watts of solar panels on the roof. We also have 8 – 420 amp-hr batteries for storage and a 3 KW inverter.

With regard to how common off-grid living is in Hawaii, it’s mixed. On-grid is typical on Oahu, Kauai and the resort areas of Maui and the Big Island. Off-grid is more common on East Maui and the rest of the Big Island.

Here’s a run down of what we did:

  • Installation of two new 175W SW 24 Volt solar panel modules, bring our tally on the roof up to 1600 watts.
  • Connection of existing solar array strings to fused PV string connector.
  • New wiring to charge controller.
  • New MS60 Outback charge controller.
  • 8 L16 High capacity 420 AH batteries
  • New battery connectors 2/0
  • Concrete slab 20″x 55″ for batteries
  • Plywood enclosure for batteries
  • Plywood cabinet for Outback 3048 sine wave inverter. (SEXY describes it well!)
  • Indoor meter to monitor battery status and Voltage or Amp draw.
  • 110 Volt Flojet pump. This replaced our old 12 Volt pump, meaning we have better water pressure now, too.
  • All wiring below the string connector enclosed in conduit.
  • New conduit run with #6 wire to house in back.
  • Connection of house in back.
  • New main breaker cabinet next to inverter.
  • Removal of old batteries and equipment.

The total cost of the upgrade (i.e., ripping out then entire old system, save a few solar panels on the roof) was about $11,000. With the cost of grid energy in Maui hovering around 40 cents per kilowatt hour, this upgrade pays for itself in three years. If the price of diesel fuel keeps rising, the break even day will come even faster. There are also the environmental benefits of not spewing diesel fumes and CO2. And by not erecting power lines, we preserve the amazing ocean views. Here’s to solar power!

Environment

Termite Tenting Sucks Lots of Water and Electricity

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Homeowners beware:  tenting for termites requires huge amounts of water and power adding expensive, hidden costs.  Termite fumigation is standard practice in Hawaii and other places with termites before a property can be sold and for routine maintenance.   Our recent experience tenting our off-grid home allowed us to see firsthand how this resource-intensive process works, without any forewarning from the company.

Most home service providers, like carpet cleaners and yard keepers, bring their own tools, fuel and water, but not termite controllers.  We were required to provide them with water and electricity for 24 hours while our house was tented and fumigated for termites.  Little do we know how much of our water and power they would use.  Here’s the breakdown:

Water

Termite treators use water to fill bags that weight down the fumigation tents after they have staked the tents.  Each of these bags requires about 10 gallons of water.  A tent for an average-sized house could use up to 100 bags.  Our 1,000-square foot cottage needed about 50 bags, or 500 gallons of water.  Think kid-sized swimming pool.

They also needed water to blow across the fans.  They turned on our spigot and turned it off about 12 hours later.  This used over 3,000 gallons of water and drained our water tank dry.  This nearly burned out our water pump.

Power

They also required continuous 24-hour electricity to power the fans and blowers.  They drew from our 7,000-watt generator and solar power system.  All together, fumigation sucked back about 100 KwH of electricity.  This is equivalent to 3-5 days extra days of power usage for a typical household in the US.  It’s like adding another week to your power bill.

Environment, food, Lifestyle

How To Make a Solar Powered Oven

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How can someone construct a solar powered oven locally? This really good question came from a reader of this blog in response to the post Solar Powered Cooking Oven. There are several good resources on building your own solar oven, and I’m going to summarize them here.

Start with a Black Box

Any kind of non-toxic, non-shiny waterproof box will work. A box with suitcase-size dimensions will allow you to use a medium-sized baking pan that is about 9 by 12 inches.

Next you will need to paint it black with a food-grade, heat-resistant paint. In a poor country, I’m not sure where you can readily find this kind of paint, but most hardware stores in developed countries sell oven paint. Paint the inside of the box thoroughly, air dry and give it a second coat. Air dry until the pain is cured and all of the gases are clear.

Add a Glass Lid

The glass lid does a few things: keeps the heat in, traps moisture and keeps critters out. Attach the glass to the box with a hinge on one side so that you can easily lift the lid. On the opposite side, attach rubber feet so that the glass will seal when closed. Finally add one or two small screw hinges or clamps that firmly hold the lid closed.

Reflectors

The reflectors gather the sunlight and focus it into your black box. You can use any sturdy outdoor material (i.e., plastic, wood, metal) as long as it’s waterproof. Cut four pieces, one the length of each side of the box and attach them to the top of the box. Cover them with a shiny, reflecting material. Aluminum foil or paint will work. Just make sure than reflecting surface is smooth and shiny.

Accessories

A few optional items will make the oven easier to use: a thermometer inside the oven, carrying handle, a swivel tray inside the box and an adjustable leg to raise and lower the oven to match the angle of the sun. If you can’t find these, the oven will work without them.

However, you need a non-reflective pan for cooking. It can be glass, cast iron or even teflon just as long as it’s not shiny. A shiny pan will reflect the heat away from your food, which defeats the purpose.

Alternatives

Another reader in India mentioned that she uses a parabolic cooking dish like the one shown above to capture sunlight and slow-cook food. You cannot fry or bake on high heat, but the design is much simpler. It is literally a curved dish with the depression in the center. So if you can’t find the materials locally to make your own solar oven, try a parabolic cooking dish.  You might even try recycling an old satellite dish, cover it with reflective material and voila!

Good luck and let me know how yours turns out!