Free Energy Closed Loop System

With winter local heating degree days at approximately 6,500, the auxiliary heat performance level was calculated at 14,404 BTUs per year, per square foot. (We found Passive Solar Design Strategies, listed in Access, very useful for making these calculations.) The actual maximum temperature swing is 8.8°F (4.9°C). On the practical side, it only took half a cord of construction scraps to keep the house a comfortable 70°F (21°C) all winter. The coldest the house ever became during an extended leave was 63°F (17°C), with outside

A garden bed stretches the length of the sunroom.

temperatures down to less than 5°F (-15°C). With local summer average high temperatures greater than 90°F (32°C), the actual high temperature for the house was 72°F (22°C) during the construction summer of 1999 and only 70°F (21°C) last summer.

Ventilation

The house was designed to provide easy internal movement of air with ceiling fans in central rooms. A whole-house, 24 VDC fan also moves air at less than 5 feet per second throughout the back rooms, and ventilates the front of the house through the transom windows. The composting toilets also have 24 VDC fans continuously exhausting to create a gentle vacuum in the tightly constructed structure.

We installed four "earth tubes" around the house. Each tube is 100 feet (30 m) of 4 inch (10 cm) PVC buried around the foundation. The intakes are located under the eave of the roof, and the other ends are in specific areas of the house. These tubes allow the gentle vacuum of the house to suck in outside air that is cooled in the summer or heated in the winter by natural ground thermodynamics. They provide a fresh air exchange every 2.5 hours. This is one of the greatest attributes of the house. We can leave for a month with all the windows closed, and when we return, the house is full of fresh air.

Electricity

Our plans included eventually having a family, so the power system was designed for expansion. Both the current setup and what is planned for the future will provide electricity through a three-day, winter storm cycle. After that, we have the propane generator as backup. We got the system up and running as soon as possible during construction, so we could shut the stinking generator off.

The system provided all the power for the house construction project. At one point during a framing weekend, we had fifteen people working. That included one table saw running almost continuously, two compound miter saws, and at least three circular saws. We were very blessed with Colorado cloud-free, blue skies, and ran the generator for only a few hours during the whole weekend.

Fourteen (of a possible eighteen) Siemens SP75 photovoltaic modules provide 1,050 watts of power.

Fourteen (of a possible eighteen) Siemens SP75 photovoltaic modules provide 1,050 watts of power.

The Ananda Power Center and Trace SW4024 came prewired and were bought used.

The initial system included a Wattsun eighteen-panel tracker with fourteen Siemens SP75 panels on it. Our plan was to add two panels per child—do you think they will understand that those two panels will only produce 825 watt-hours per day of juice in the winter?

The tracker is located with unobstructed, sunrise-to-sunset access to get full use of the available sun. In the summer, we generally turn the tracker off and leave the rack aimed at high noon, since we have a surplus of energy then. In the winter, I believe it really pays to get

Inside the Ananda Power Center you can see the main pullout DC disconnect, DC breakers, and the backs of the TriMetric and Smart Charger.

every minute of sun. During storm cycles, the sun only shines from 7 to 10 AM, but those three hours are enough to keep all those extra winter loads running.

The heart of the system is a used Ananda Power Center and a Trace SW4024 inverter. Power centers are worth every penny to a self-installer like me. The manuals were fantastic, and everything was already labeled. Buying a used inverter and power center saved some cash, but the big advantage was that the power center was prewired. The TriMetric meter has proved very useful. During the winter months, we have to be careful with our energy usage, and the meter tells the story.

The power center, inverter, batteries, and generator are located in the water storage room of the shop building. I put them all together so the mass of the water could keep the batteries warm during the winter. We also installed a digital volt meter in the utility room of the

LeFevre Solar-Electric System Costs (1997)

Item

Cost (US$)

14 Siemens SP75 panels

$4,480

Used Ananda Power Center, Trace SW4024 inverter, & TriMetric meter

3,400

Winco 9,000 watt, tri-fuel generator

2,120

Wattsun 18 panel, dual-axis tracker

1,875

16 Trojan T-105 golf cart batteries

0 0

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