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Office-Sized Solar-Electric System for Renters

Eric Grisen

©2003 Eric Grisen

Do you want to live with renewable energy, but don't think you can because you're renting? You can. With a little creativity, you can design and install a solar-electric system that has minimal impact on your rented house. We did!

This renewable energy system is big enough to power a home office, but it's small enough to live in a closet or travel in the back of a pickup truck.

This renewable energy system is big enough to power a home office, but it's small enough to live in a closet or travel in the back of a pickup truck.

Last year, my partner Tiffany and I turned on a 300 watt photovoltaic (PV) system to power my home office. We were able to install the system with minimal impact to our rented house—six lag screws into our patio's roof, and one hole into my office's ceiling. We also designed the system to be portable, so when we moved, we were able to pack it into our pickup truck in a matter of hours. You can build a system like this for less than US$4,000.

Our photovoltaic (PV) system powers the equipment I need for my telecommuting job at Home Power, including a Macintosh G3 desktop computer, Radius 21 inch CRT monitor, Aiwa boom box stereo, Umax Astra 2000U scanner, and an APS Pro 18 GB external hard drive.

Energy Efficiency First!

Before we installed the PV system, we applied lots of energy efficiency measures to our rented house. Why is that important? If part of your motivation is to have a lighter footprint on the planet, it makes sense (and cents) to reduce your energy consumption first. Inexpensive, even free, energy efficiency steps (like turning off appliances when you're not using them) result in a decreased daily energy requirement, and a smaller and less expensive PV system.

For example, by replacing our heat-producing, 100 watt, incandescent lights with cooler, compact fluorescents, we reduced our household lighting load by 70 percent. We further reduced our electrical load by turning our electric water heater way down, and wrapping it with an R-9 insulating blanket. Sensible energy conservation and modest consumption have always kept our utility bills relatively low. But in our all-electric suburban house that we were renting, we were unable to use less than 10 KWH a day on average.

Load Analysis

For our PV system to make sense to us, it had to be big enough to power all the loads in my office. If the system could cover my office's loads, it would give us to the flexibility to live off-grid, and I'd have enough electricity for my telecommuting work at HP. It would also be a good beginning to a home-sized system.

To find out how much energy all my computer equipment uses, I did a load analysis. Using a Brand Electronics digital power meter, I measured how many watts each appliance draws (see load table). I did this by plugging them into the meter, and then plugging the meter into the wall. The meter's kilowatt-hour (KWH) figure, recorded over a 24 hour period, allowed me to determine the average daily watt-hours used by each piece of equipment.

After I recorded the data from the individual loads, I gave myself a reality check by plugging the whole workstation's plug strip into the meter. This confirmed the individual measurements. My entire computer system uses about 1.3 KWH a day, or 6.5 KWH in a five-day work week. This is the amount of energy we wanted our PV system to cover.

The load table shows how I calculated how much energy my office uses. I learned this method from Solar Energy International (SEI). If you don't have a power meter, you can use the wattage information published on the appliance's label. But keep in mind that these figures represent the maximum draw of the appliance. Actual power requirements are typically lower, often substantially. By calculating or measuring exactly how many watts each appliance draws and multiplying it by how many hours a day it gets used, you can come up with a total daily kilowatt-hour number.

System Design

After the load analysis, we looked at other project considerations as we designed the system. The system had to be easy to move, have low impact on the house, and stay within our budget. It made sense for us to build the smallest system we could and then expand it later. After all, we do live on the grid. If the system can't keep up with my office usage, I can always plug into the wall for a little juice from the utility grid. We designed the system so that it would at least power my office's loads in the summertime.

Grisen System Loads


Home Business Models Exposed

Home Business Models Exposed

Home business is the way the world is going to go in the near future. Gone are the days when people slaved over their office desks. This is the age where the concept of career liberalization is really going togain root.

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