The Renewable Power System for the Experimental House 0

Our "Power Center" with inverter, battery bank and charge controller

Our "Power Center" with inverter, battery bank and charge controller

A solar powered home presents a unique set of challenges for the designer. The home relies for its power on weather conditions, which are highly variable from site to site and even from year to year. The technology is still fairly costly so designing a system with high reliability often comes at a cost that makes it no longer price competitive with grid tied options.

Many engineers, scientists and homeowners have tackled these challenges to provide effective designs for their applications and geographic location. Solar power system design must take into account the local solar radiation that is available and your actual power needs.  If wind resources are good, a wind generator may also be an option.  A wind generator is a good complement to solar for an off-grid house because, with the shorter days, there is less solar available during the winter but it is usually windier in the winter.

A stand-alone off-grid renewable power system has five basic components:

1.  A charging system, consisting of a solar panel array or a wind generator or both.
2.  An energy storage system, generally a bank of deep cycle lead-acid batteries.
3.  A charge control system, to prevent overcharging of the batteries.
4.  An inverter to convert low voltage DC to 110 V AC to power normal household loads.
5.  A backup generator operating on gasoline, diesel, natural gas or propane.

Schematic Diagram of the Solar and Wind Power System

Schematic Diagram of the Solar and Wind Power System

The effectiveness of the total system depends on the availability of solar radiation and the wind speed distribution at the building site and the load requirements of the home.  The battery system should be able to run the house for at least 3  days when absolutely no charging available.  Since there will always be some solar charging during the day (even when it’s snowing) this effectively gives you at least 4 days – usually you have 5 to 6 days of reserve power.

The complete system design that we used for the experimental house is shown in the schematic diagram below.  We chose an 8 panel solar array and a 1 kW wind turbine for the charging system, a 1314 AH battery bank for storage and a 4000 Watt inverter.   We also have a battery status meter that shows what we are charging at, what our voltage is and how many amp hours (AH) we have used from our battery bank.  It’s very useful to know what is going on with your system!

The EZ-Wire System Center, included with the Whisper H80 wind generator, is shown in block form in the diagram. The center provides bonding blocks, wind generator brake, solar array disconnect, dump load and the rectifiers and power supply circuit to provide the 24 VDC output for battery charging.  The system monitor and charge regulator is included in the same interface.

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