Tuesday, July 29, 2008

PV System Performance Update

People sometimes ask me how much I save on my electric bill since installing solar panels. I have some difficulty answering that question. While my grid-supplied electricity usage is about 50% less than it was two years ago, much of that is due to energy efficiency improvements I’ve made. Replacing my refrigerator and switching to CFL lights contributed in a big way to cutting electricity usage. Still, my PV system has made a significant contribution and it’s good to evaluate performance now and then.

About my system:

My system can be considered small. If this were my only source of electricity I would be quite limited in the appliances I could use. Although some folks rely on PV systems much smaller than mine to meet all of their needs for electricity, my family prefers not to live with such limitations. I’ll continue to use electricity from the power grid, and continue to enlarge my system as my budget allows. I plan to add 1 or 2 more solar panels before the end of this year, and perhaps 2 more next year. I would like to be able to use wind or hydro, but those options are not practical for my location. Solar fits nicely into my budget, unlike more elaborate solutions such as hydrogen generation.

System specifications and capabilities:

I have 425-watts of PV panels on my roof.
My main battery bank is rated at 630ah.
My spare battery bank is rated at 420ah.
The typical load is a chest freezer, and a refrigerator.
When neither compressor is running, the load can be as low as 5 watts.
The maximum load sometimes exceeds 525 watts.
The system is automated. The load switches to grid-supplied power when batteries are low.

With about 4 hours of sunlight per day, I expect 1700 watt/hours of electricity production.

At 65% efficiency, I should get 1100 watt/hours from the system each sunny day.

My refrigerator and freezer need about 3.6 kilowatt/hours per day for their operation, much more than the PV system can generate. I could have provided a smaller load, but by connecting a load greater than the system can handle I’m not wasting any of the power that the system is capable of producing.

Measured results:

For the month of June, my solar panels delivered 42kwh to the batteries and load, an average of 1.4kwh per day.

My data also shows that I’m sending about 2kwh to the loads each day, more than the solar panels produce. The apparent discrepancy is due to the fact that I top off the charge on my batteries at night with a battery charger. My utility-provided electricity has been very inexpensive at night, and I take advantage of that by storing the low-cost energy for use during the day when rates are higher. This opportunity will end in the fall, when daytime rates go down, and nighttime rates increase. You can learn more about this plan at www.powersmartpricing.org.

When the grid fails:

My day-to-day strategy is to use as much of the solar-generated power as I can for household use, cutting my electric bill. My strategy changes dramatically when grid power fails. Since I don’t have enough capacity to keep my big refrigerator running, I unplug it. I place all of my frozen food in the chest freezer. I place items from my refrigerator in ice-chests, and use ice that I’ve previously stored in the chest freezer. My PV system can keep the chest freezer running continuously, as long as I have plenty of sunshine. I use CFL’s for light, watch TV and listen to the radio, use the microwave oven, charge the cell phone battery, and do most of the other things I would normally do with grid-supplied power. I just have to use this limited supply of power more conservatively.

Winter is the worst possible time to suffer from an extended grid power outage. To conserve electricity, I heat only a portion of my home using my corn-burning stove. Eventually I’ll have a solar PV system big enough to keep the stove running 24/7, but I’m not quite there yet. My system is big enough to meet my summertime needs, but using central air-conditioning is not possible. I have plenty of energy during mild weather grid-power outages, and I’m very comfortable in my home when that happens. It’s a joy to have plenty of light, to be able to use a TV and appliances, and to prepare food while many of my neighbors are using candles. I must admit that I still have a small gasoline-powered generator, but I’ll phase it out as my PV system grows.


I’ll soon be installing another solar panel, and I have a couple of system modifications in mind that I expect will improve overall system efficiency. Starting small has been a rewarding experience for me, and I would highly recommend it to others. You might be surprised by how much you can benefit by implementing a small PV system, and you’ll certainly learn a lot. Each system upgrade makes you more independent, and improves your comfort level in the event of a grid power failure. Producing your own electricity will lead to using less gasoline. By using less gasoline you’ll be sending less money to those who want to kill you or convert you to Islam against your will. For each kwh of grid-supplied power that you don’t use, about 2.2 pounds of carbon dioxide is kept out of the atmosphere, not to mention other pollutants emitted from coal-fired power plants. If many of us do a little, it will help a lot.


Tuesday, July 22, 2008

Future USA

George W has a horrible environmental record as president, but his Texas ranch is off-grid with a variety of renewable energy systems. Although he’s done little to prepare the country for the effects of declining fossil fuel, he hasn’t neglected his own needs. Does he know something about the future that the rest of us don’t? We see skyrocketing gasoline and food prices, but we tend to plan for the future as if we expect things to be pretty much the same as they are today. Are we in a state of denial about our future?

Perhaps we’re all in a state of denial, even large corporations. GM spends an enormous amount of money promoting big cars and trucks, while closing several of its assembly plants due to lack of sales. Shouldn’t they have seen this coming? Why did they let Toyota and Honda take the lead with their fuel-efficient vehicles? GM continues to push it's gas-guzzlers by offering discounts and rebates, even offering to pay a portion of your gas bill. They use slogans like “Let’s Refuel America”. It seems that they’re determined to use up all of the remaining fossil fuel as quickly as possible!

Banks are in trouble, and I wonder why so many of them have been willing to make loans to people who probably won’t be able to keep up with the payments. Again, shouldn’t they have seen this coming? We shouldn’t be shocked when we find ourselves in a society that is much different than the one we live in today. Unlike some car manufacturers and banks, we should see this coming and prepare for it. We already drive less today because of the high cost of gasoline, but we still drive. We’re learning to economize as food prices go up, but we still buy food of course. Today most of us can compensate for rising food and gasoline prices by cutting back here and there, but what will we do if things get worse?

While another terrorist attack could trigger a sudden collapse of our economy, we might suffer more from a gradual decline. If your cost of living outpaces your income long enough, you’re in trouble. You may think that these gloom-and-doom scenarios are unrealistic and choose to do nothing, but if you believe that the worst is yet to come you should prepare as soon as you can. If you wait until things get worse, it will be too late. You’ll be forced to use the renewable energy systems you have in place, not the systems you planned to install someday.

Once you’ve decided to prepare, the next question is “How do I prepare?” How you prepare depends on how you want to live, and on your budget. You might choose to prepare for a total melt-down of society by considering your basic needs, or you might opt for a strategy that attempts to maintain your lifestyle as it was before the melt-down. A reasonable approach would be somewhere in between. Since everyone’s goals and budgets are different, this article is not a one-size-fits-all design guide. Instead, these are some ideas to help you formulate your own plan.

You can probably live as comfortably as you do now, and use half of the resources that you’re currently using, if you’ll simply cut waste. Start by eliminating phantom loads. Put your TV’s, and other items that continue to use power when turned off, on power strips. Get used to powering these items on and off with the power strips on/off switch. Get rid of unnecessary items like hand-lotion warmers. When possible, replace electrical items with mechanical items that serve the same purpose. Alarm clocks, can openers, and doorbells are a few examples. If you haven’t done so already, replace your incandescent light bulbs with compact fluorescents (CFL’s). Replace old and inefficient appliances, especially your refrigerator. Consider energy-saving home improvements, such as adding insulation and replacing inefficient windows and doors. These things not only help to cut your energy costs, they are a logical prerequisite to implementing alternative energy systems in your home. Having done those things you can get by with a smaller photovoltaic (PV) system, but you’re still not fully prepared to deal with a serious energy crisis. Let’s go beyond the basics.

Do you heat and cool your entire house 24/7? You could cut your heating and cooling costs dramatically if you were to heat and cool only the area’s that you’re using. Is a 14’ by 14’ bedroom really necessary? Couldn’t you sleep just as well in a climate-controlled 6’ by 9’ space? Providing climate control to a much smaller space requires less energy, making it possible to get by with a smaller photovoltaic (PV) system. If you have an unused room in your home, perhaps an unfinished basement with a window, you can easily create a living environment that requires little energy. You can be just as comfortable in a small well insulated space, perhaps with the aid of a window air conditioner or an electric blanket, as you are now in your big bedroom. If you’ll make the necessary adjustments you’ll be able to meet your energy needs with a small PV array, instead of covering your entire south-facing roof and spending $25,000.00. I’ve determined that I can meet my own basic needs with as little as 800 watts of PV panels, and a total investment of less than $6000.00. With 4 hours of sunshine, a system that size can generate 3200 watt/hours each day (not taking into account system losses and inefficiencies). A big portion of the energy I produce will be used to keep a small chest freezer running. I’ll also use cfl’s, radio and tv, cell phone charger, microwave oven, and fans. I’ll have limited use of my corn-burning stove or a window air conditioner. I can summarize my minimum needs as shown below:

Mild Weather Energy Requirements: 1220 watt/hours per day

Hot Weather Energy Requirements: 2530 watt/hours per day

Cold Weather Energy Requirements: 2990 watt/hours per day

If I build a system that barely meets my cold weather requirements, I’ll have shortages on cloudy days. I’ll need to cut back at times. But a system designed to meet my cold weather requirements will give me a surplus of electricity during mild and warm weather, allowing me to use other appliances to a greater extent. I’ve learned techniques that help me get the most from a small system. For example; if I place my chest freezer in the coolest portion of the house, it uses less energy for its operation while providing some heat to that area. I don’t run my refrigerator when the power fails; I use an ice-chest instead. My freezer, which is powered by my PV system, provides the ice.

As you make your plans, don’t neglect your basic needs. You’ll need fresh water on an ongoing basis of course. You might want to visit one of the many survivalist websites for information and ideas along those lines.

Since your need for food is an ongoing one, knowing how to grow and preserve vegetables and fruits is a skill that will serve you well. If you’re already a gardener, enlarge your garden. Tomatoes and other veggies are easy to grow, and easy to preserve. By canning your vegetables, you’ll have a supply of food that doesn’t require refrigeration. It’s a good feeling to know that an extended power failure (or a failure of your PV system), won’t ruin a big portion of your emergency food supply.

“Perhaps the day will come when the United States is no longer addicted to imported oil; but that day is still many years off. For now, the reason for America's rapt attention to the security of the Persian Gulf is what it has always been. It's about the oil.” Ted Koppel

Fighting for control of every last drop of oil is the foundation of this administration’s energy policy, and it will not end well. To the extent that we can, let’s not support this policy. Mass acceptance of renewable energy systems by the general public will show our elected officials, and the rest of the world, that we want to do the right thing. We can do it. We should do it. Future generations will appreciate our efforts.


Monday, July 14, 2008

My Renewable Energy Projects, an Update

Solar Water Heater:

My solar swimming pool water heating project is still a work in progress. I now circulate water through 200 feet of pvc tubing mounted in the attic of my storage shed. I pump cool water from the pool, circulate it through the pvc heat exchanger, and return the heated water back into the pool.

The system heats the water nicely, but I seem to have too much pool for the small amount of hot water I’m producing. I’m using an ordinary garden hose for the water input, and it has a tendency to collapse under the vacuum that the pump creates. This restriction lowers the output of the system. I may put this project on hold, since heating the pool water is not necessary this time of year. I suppose I'll work on it again this fall, or next spring.

Home Heating with Corn:

My corn stove saw limited use last winter due to the high cost of corn. Corn was about $2.50 per bushel when I installed the stove, but it’s currently about $7.00 per bushel. The sharp increase was due to the huge demand for corn by the ethanol industry. I expect the cost of corn to decline as cellulosic ethanol plants come on line, and I’ll once again be able to economically use the stove.

If the price of corn remains high, I might try growing it myself (again). I've recently purchased my first piece of equipment to help with the process, an old corn sheller. I found the sheller at an antique store. This should be well worth the 20 dollars I paid for it.

My PV System Automation and Battery Charging:

Summer has arrived, and hot weather has resulted in an increased demand for electricity. My utility rate plan has me paying for electricity based on demand, and the rate has exceeded .17 per kwh a few times. However, my nighttime rates have been surprisingly low, sometimes below .01 per kwh. To take advantage of this large discrepancy, I sometimes charge my batteries at night and use the stored energy to run my refrigerator and freezer during the day when utility rates are high. It seems that switching to a variable electricity rate plan has paid off, and that my load shifting plan is working. Here are some statistics:

My cost for the electricity I used in June of 2008 was $65.38.
My cost for the electricity I used in June of 2007 was $116.31.

I used 625kwh of electricity in June of 2008.
I used 1127kwh of electricity in June of 2007.

Other PV System Statistics:

I currently have 5 – 85 watt PV panels on my roof. I’ve not yet adjusted the angle for the summer sun, so they’re not pointed at an optimal angle. I waited a little too long to do this, and now I want to avoid walking on the roof while the shingles are hot. Later this year I’ll add another PV panel, and I’ll adjust the angle at that time.

In addition to the inefficiency caused by a less-than-ideal angle, I’ve noticed the effect of temperature on the PV panels. I seldom see PV panel current exceed 22 amps. I’ve seen panel current exceed 25 amps during cold weather.

System output averages a little more than 2kwh per day, or about 10% of my total household usage, but that is with a boost from the battery charger. I’m pretty happy with this free, and low-cost, electricity.


Some say that unless utility rates are exceptionally high, and renewable energy incentives are exceptionally good, the payback for a solar PV system might be in excess of 25 years. But for those of us who do most of the labor ourselves, and explore ways to improve efficiency, payback can be much quicker. At the same time we benefit from a system that shelters us from utility failures. We can stay comfortably in our homes at a time when others need to abandon theirs. We can keep our refrigerators and freezers running, protecting our food from spoiling. We can keep our communications and entertainment equipment working, and protect our property and belongings. I don’t dwell on the payback period. My system has already paid for itself as far as I’m concerned. My systems can keep me comfortable in my home regardless of outside weather, or disruptions of any of my utilities. My systems are far from complete, but are improving with time. In the not-to-distant future I’ll be able to cut my transportation expenses thanks to my PV system. Perhaps one of these days I’ll be able to pull the plug on all outside services.


Monday, July 07, 2008

Transportation Alternatives That Make Sense

Most of us can’t afford ocean-front property, so we take vacations. Most of us can’t afford a luxury yacht, so we charter cruises instead. Most of us can’t afford to own an airplane, so we book flights with commercial airline companies. We tend to use common sense for most of our travel, but many of us drive vehicles that greatly exceed our needs. While our day-to-day needs might call for a vehicle that is capable of taking one person on a 20-mile round-trip work commute, we often end up with a much larger vehicle. We buy these larger vehicles because we sometimes need the extra capacity. We need the extra capacity to haul hardware or appliances, to take the family on a camping trip, or maybe to tow a trailer or boat. We may only need the extra capacity 1% of the time, but we end up using a vehicle that burns an excessive amount of gasoline every day. This excessive use of gasoline is not only expensive, it’s bad for the environment and a waste of natural resources that are already in short supply. Excessive use of gasoline feeds the greediness of oil companies, causing gasoline to be even more expensive for all of us.

Do you drive a gas-guzzler?
At today’s prices you could be
spending $40.00 for 400 miles
of driving, instead of $140.00
to go the same distance.

The automobile industry thought it could address the problem by making large vehicles more fuel-efficient, but had to reconsider when people stopped buying large vehicles. Consumers understand that while a fuel-efficient SUV might get 20mpg instead of 10, they are better off driving a smaller vehicle at 35mpg or more. Many of us would be better off using a gas-efficient vehicle for our daily commute, and renting a larger vehicle when extra capacity is needed. A fuel-efficient vehicle might save the owner $2000.00 or more in gasoline per year, more than enough to pay for the rental of a larger vehicle for those times when it’s needed. A hardware-store in my neighborhood has truck rentals at a cost of $20.00 for 90 minutes.

If you need to haul small loads often, frequent large vehicle rentals might not be the best strategy for you. A small utility trailer might be your best choice. Even the smallest of cars can tow a lightly-loaded trailer easily. You’ll need to install a trailer hitch, add a connector for lights, and you’ll need to license the trailer, but you’ll save in the long run.

My strategy is to avoid using the family mini-van as much as possible, but I could do better. I would much rather co-own a mini-van or truck. If several families owned a large vehicle, each of them could use it for a few days each month. The purchase cost, as well as the cost for licensing and insurance, would be much less if those costs were divided among several owners. Many of us don’t need a large vehicle for more than a few days each month anyway.

This co-ownership plan could be easily expanded to include more than one vehicle, helping to ensure that plan participants would get the type of vehicle needed, when they need it. For example; 16 families could co-own 2 vehicles. One could be a pickup truck, and one could be a mini-van. Scheduling could be done via the Internet, and all participants would have instant access to vehicle availability information. Payment plans could be tailored to meet the needs of each participant, ensuring a fair deal for each member of the group. Some two-car families could benefit from this plan by becoming one-car families.

I’ve thought about my own needs, and my ideal plan would include the use of a mini-van for about three weeks each year. This would allow me to take my family on a two-week vacation, and a couple of weekend get-a-way trips. I’ll also need a pickup truck about 21 times each year to haul building materials, garden and landscaping supplies, appliances and furniture, and corn for my stove. If everyone in the plan has equal access, each of the 16 participating families will have just over 42 days of vehicle availability each year. A potential drawback of the plan is that participants would tend to want the vehicles on weekends, and not so much during the week. This problem might be minimized by careful selection of plan participants. A retired couple might be happy to use one of the available vehicles during the week for shopping, leaving it free on the weekends for family outings. Such arrangements could be specified by plan clauses.

There are many ways a co-ownership plan could be implemented. Several families could co-own an old beat-up pickup truck for example. After purchasing an inexpensive vehicle outright, insurance and maintenance would be the only ongoing cost. This would be a dirt-cheap solution for each family involved.

Co-ownership may sound like a radical idea, and the car rental agencies are going to hate it, but it’s an idea whose time has come. The best implementation would be on a neighborhood-by-neighborhood basis, providing quick and easy access to vehicles with little advance planning.