Wednesday, October 31, 2007

Are You Ready for a Winter Emergency?

Winter is almost here, and that brings back memories of last years extended power failure. It was obvious at the moment the failure occurred that this was going to be a worst-case scenario. With sub-freezing temperatures outside, I knew it wouldn’t be long before it would be unbearably cold inside. Fortunately I had plenty of corn on hand for the corn-burning stove, and electricity available from my small off-grid photovoltaic (PV) system. We survived the first night comfortably, but I knew the PV system would not be able to keep up with the electrical demand of the stove.

That power failure taught me a valuable lesson. When the grid fails, you use the systems you have, not the ones you wish you had. And although that may sound obvious, you’ll understand the significance of that statement once you’ve experienced it for yourself. You’ll find yourself wishing you had installed eight PV panels instead of four, and you’ll wish you had a bigger battery bank. As you make do with what you have, you’ll vow to make the needed upgrades before the next emergency.

My PV system was too small to supply the electrical needs of the stove and the chest freezer last winter, so I purchased a small gasoline-powered generator. I was fortunate in that the electrical outage was spotty, and I only had to drive one mile to find a source of gasoline. With winter approaching once again, this is a good time to assess preparedness.

When last-year’s power failure occurred, I had 2 PV panels (170-watts of PV), while now I have four panels (340-watts of PV). I still have the same amount of batteries, a total of 420ah. In practical terms this means that I can charge my batteries faster, but I have no more storage capacity than I did last winter. Based on my previous experience, I should be able to run the stove for at least 8 hours, but I may be able to fully charge the batteries with only one day of sunshine. Previously, it has taken two days. This means, of course, that I could have as much as eight hours of heat per night, every night, as long as the sun shines during the day. That’s great progress, but I obviously need to do much more.

I’ve recently replaced my 20-amp charge controller with a 60-amp one, paving the way for additional solar panels. I’m very pleased with my 1100-watt sine wave inverter, so no upgrades are needed in that area. My goal before the end of the year is to add at least one more panel, and another 210ah of battery capacity. In addition to the electrical demands of the corn stove, being able to run the chest freezer means that I can keep food from spoiling. Additionally, I’ll need lights, the ability to charge a cell-phone, and the limited use of other household appliances.

Because my system will remain small in the short term, I need to incorporate other strategies in the event of an extended power failure occurring in the winter. Closing off unused rooms is one way I can cut back on heating. I can use an electric blanket, and therefore tolerate cooler indoor temperatures as I sleep. Instead of running a refrigerator, I'll place perishables in an ice-chest, and use an energy-efficient chest freezer. While these inconveniences are annoying, at least I can remain relatively comfortable in my home. Some of my neighbors had to abandon their homes during last-years power outage. With each system upgrade, living through an extended power failure becomes less of an annoyance.


Monday, October 15, 2007

PV System Upgrade

While I’m looking forward to adding PV panels to my array, I’ll first have to replace my 20 amp charge controller with a bigger one. After careful consideration of available products, I’ve selected the Morningstar TriStar-60. I considered the Outback MX-60, but decided that the TriStar would be a better choice for my small system.

The Outback is a maximum power point tracking (MPPT) charge controller, which means that it can convert DC voltage to a higher or lower value. In some cases, this can result in more efficiency, but it probably wouldn’t benefit me much because my PV array is small. The TriStar is a pulse width modulation (PWM) charge controller, and it charges batteries in four stages. The strength of the charging signal is controlled by varying the pulse width. This has proven to be an efficient charging scheme for small systems.

The Outback charge controller can match any common PV array voltage to any common battery voltage. This feature allows the user to economize on wiring, and minimize losses that would otherwise occur. The TriStar can operate at 12, 24, or 48 volts, but cannot convert a high PV panel voltage to a lower battery voltage as the Outback can. While the Outback MX-60 is also a four-stage charge controller, its dc voltage conversion feature would not benefit me greatly, considering the limited wiring options I have with my small system.

The TriStar-60 uses less than 20ma (0.02amp) of current for its operation, much less than the Outback, an important consideration for a small system. More of the solar-generated power will be applied to the load. And the TriStar-60 comes with a 5-year warranty, while the Outback MX-60 controller is only warranted for two years.

Perhaps the most interesting feature of the TriStar-60 is its digital meter (option). I’ll be able to monitor system performance more easily, and I’ll return my digital multimeter to the toolbox where it belongs. In addition to instantaneous readings, the TriStar-60’s meter can display performance over time (data logging), and remote monitoring via the Internet is possible.

Before the year ends I’ll install at least one more solar panel. My ultimate goal is not only to power my home with PV-generated electricity, but to eliminate my use of fossil fuels entirely. I already burn corn to supplement natural gas heating, and I hope to purchase a plug-in car (PHEV) within the next two years. Using cfl lighting and replacing old appliances are other ways that I’m moving closer to my goal. I might just be the first person in my town to accomplish this. How cool is that!


Tuesday, October 09, 2007

Environmentally-Friendly Products - Are They Any Good?

The energy crunch of the 1970’s resulted in a sudden influx of alternative products, many of which did not perform as advertised. As a result, the public was left with a perception that alternative products were not as good as traditional ones that serve the same purpose. Sadly, it seems that many environmentally-friendly products currently available also fail to live up to their advertised claims, and it’s easy to understand why the general public is slow to accept them. Here are a few examples:

Compact fluorescent lights:

I’ve experienced a high failure rate on the cfl’s used in my bathrooms. Perhaps the frequent on/off cycles shorten their life. I’ve cut my electric bill, but I’m not sure I’m really saving money or helping the environment due to the frequent cfl failures I’m experiencing.

I’ve observed that a cfl takes a minute or two to reach full brightness, but I’m not troubled by this. I use 19- to 25-watt cfl’s in locations where 13-watt cfl’s don’t supply enough light.

Energy-Star-rated appliances:

I suspect that Energy Star ratings are similar to gas mileage ratings on cars. We never achieve the posted gas mileage in real life, and we’ll never achieve the posted killawatt/hour per year figure posted on our Energy Star-rated appliances. I’ve tested my new refrigerator with a Kill-A-Watt meter, and found that it uses nearly twice as much energy as the Energy-Star tag says it should. I suppose that it might approach the posted rating if I seldom opened the refrigerator door, but that certainly isn’t practical. Or perhaps the energy use will be lower this winter, when it’s cooler in the house. While I am pleased that my new refrigerator uses much less energy than my old one, I wish that the ratings were more accurate.

Tankless Water Heaters:

While some people love them, my personal experience was not good. My contractor had little experience with tankless water heaters, and that’s where the problem began. I was willing to accept the high cost of the unit itself, but was unaware of the additional costs that I incurred when the unit was installed. I learned that I couldn’t simply tie-in to the existing furnace flue, I had to run a separate one using expensive stainless steel fittings. Then, I found that the unit would only produce a trickle of hot water. This problem was due to an insufficient supply of natural gas. For safety reasons, increasing the natural gas pressure was not an option. I was going to need a separate gas line from the meter to the water heater. Another option was to use several smaller tankless heaters, each one installed near the point of use. Instead, I decided to send the unit back, and return to a traditional water heater.

Washing Machines:

According to Consumer Reports, the U.S. Department of Energy now requires washers to use 21 percent less energy. Cleaning ability was compromised in order to meet those goals.

Terror Free Oil is not a product, it’s a company dedicated to purchasing oil only from countries that don’t export terrorism. Unfortunately, this well-intentioned effort will not work. It doesn’t matter where we get our oil from; the amount we use is the problem.

Products that DO work:

My corn-burning stove is one product that I am pleased with. Not only is it good for the environment, I’ve significantly reduced my home heating costs. See previous blog posts on this topic for details.

Since I’m trying to power my home with PV I’ll continue to use cfl’s and energy-efficient appliances to lighten the load. These measures allow me to get by with a smaller PV system, and in that context I am saving money.

Please feel free to comment on my observations, and add to the list based on your own experiences. Maybe this article can be the start of a renewable energy product database. After all, there are many sources of information, but few of them are unbiased.


Monday, October 01, 2007

Off-Grid vs. Grid-Tied, My Survey

By more than a two to one margin, visitors to my blog prefer grid-tied over off-grid. This came as somewhat of a surprise to me. I expected more people to opt for off-grid. I thought that being self-sufficient and having a reliable source of electricity would have steered more folks toward an off-grid system. I chose off-grid because of budget constraints, and because of an unreliable grid. I was able to build a “starter” system on a small budget, and as a result I have a limited amount of power when the grid is down. My goals were; to avoid being in the dark, to have the capability to keep warm in the winter and cool in the summer, to keep food from spoiling, and to have the limited use of other appliances. I’ve already met those goals to a certain extent. My small system can’t keep up during temperature extremes or during extended periods of cloud cover, but its benefits are impressive nevertheless when considering the size of my investment. And it’s always exciting when I upgrade the system and extend its capabilities. (I don’t know how I’d amuse myself if I were rich).

If money were no object, I’d opt for a grid-tied system with batteries. While such a system provides the best of both worlds, it is also the most costly. A grid-tied system with batteries must be able to automatically disconnect from the electrical grid when the power fails. If not, it could be dangerous for utility workers in the area. As a major advantage of such a system, it uses all of the free-power available, only switching to costly grid-supplied power as a last resort. Switching is automatic, based on setup parameters. The system can be set to be very gentle on the batteries, extending their life, or be set to use them to a greater extent, resulting in a lower electric bill. It must be great to have choices like that!

I think it’s reasonable to assume that while grid reliability problems may increase in the future, the grid is never going to disappear completely. As long as it is there part of the time, those attached can take from it and contribute to it. And those who supply power to the grid are paid, or at least credited, for their contributions. So unless electric rates or grid-connection charges are prohibitively high, being grid-tied makes more sense from a financial standpoint than an off-grid system does. And since an off-grid system with batteries efficiently uses the energy generated by the sun, it’s a good “green” choice.

While a batteryless grid-tied system is efficient and cost-effective, it must be embarrassing to have a large PV array, but no power when the grid goes down. What would the neighbors think? Still, this type of system is the best “green” choice, and it requires the least maintenance. On the other hand, I like my independence. If I could disconnect from the grid completely, I’d do it, even though that is not the most economical way to go. Unused power is wasted, so it’s a challenge to use as much of it as possible, while not stressing my batteries. I like the idea of using free energy from the sun, and not from a coal-burning power plant. I’m being kind to the planet, and preserving natural resources for future generations. Perhaps even more importantly, I’m setting a good example. Some things are more important than saving money.