Thursday, February 22, 2007
Critics of the plan have a variety of concerns, but the bottom line is this; the homeowner pays nothing until the equipment is installed and functioning. Therefore, if CitizenRE were to fail before the installation, the homeowner loses nothing.
CitizenRE is perhaps the first to offer a PV system rental plan, but others are not far behind. Information about another innovative plan can be found here:
While CitizenRE plans to manufacture solar panels and inverters, others offering similar plans will no doubt use off-the-shelf equipment with a good track record for performance and reliability. Manufacturing quality panels and inverters is a daunting task, and no one really knows if CitizenRE is up to the challenge. A rush to get equipment built and installed might result in system reliability problems.
It’s interesting to contemplate what would happen if CitizenRE were to fail after the equipment is installed. The homeowner will have over $20,000 worth of electricity-producing equipment that may stop functioning. If the homeowner could take legal ownership of the equipment, it might be possible to replace the CitizenRE-supplied inverter and control equipment with off-the-shelf components, restoring system functionality. That modest investment would allow the homeowner to use power from the already installed solar panels, while paying nothing for the electricity that the system generates. To some, however, the thought of maintaining this high-tech equipment would not be appealing.
I’m sure we’ll be hearing more about CitizenRE in the future, and it will be interesting to see how this plays out. The reputation of the solar energy industry can be hurt by an influx of poor quality equipment and by poor performance by a major player. Let’s hope that CitizenRE is up to the challenge.
Here is the link to the CitizenRE website: http://renu.citizenre.com/
You’ll find a podcast and interesting comments here: http://www.renewableenergyaccess.com/rea/news/podcast;jsessionid=BFE8544505085AFEBE7235397D0949A9?id=47452
Thursday, February 15, 2007
While the summer sun appears almost directly overhead at mid-day, winter sun appears to the south. The drawing below shows the sun’s position, and the approximate best angle for roof-mounted panels for the summer and winter seasons.
To determine the optimum angle for your solar panel for each season, you’ll first need to know the latitude for your location. You can find that information here:
The website listed below allows you to enter the latitude for your location, and then calculates the optimum angle for each of the twelve months of the year:
While you probably don’t want to change the angle every month, changing it two to four times per year will improve the performance of your array. Using data for my location, I’ve decided to use a 25 degree angle for spring and summer, and 50 degrees for fall and winter. Since my roof is already at a 17 degree angle, my panel mounts need to make up the difference, or an additional 8 degrees for the spring and summer position, and an additional 33 degrees for fall and winter. To measure the angles, I’ve purchased the tool shown below from my local hardware store:
I made my panel mounts using 1” X 1” X 1/8” angle aluminum. I start by cutting two long pieces, one for each side of each panel. I securely mount those to the frame of each solar panel. I then cut the top and bottom legs, and the feet. I’ve decided to make the bottom legs three inches in length. Elevating the panels three inches above the roof allows plenty of air to circulate under the panels, keeping them from overheating. This is an important design consideration because solar panels loose efficiency at high temperatures. The upper legs, as shown in the photo below, are 8” in length. The difference between the length of the lower and upper legs results in the additional 8 degrees of tilt that I need for my summer configuration. Longer upper legs will be used in the fall and winter months. While only two panels are shown here, additional panels can easily be added along side the others. To do that, the legs between the panels need to be modified slightly.
Legs are attached to 3” feet, made from the same aluminum angle stock. I used 2 ½” stainless steel lag screws to securely mount the assembly to the roof. To prevent leaks, I’ve used a generous amount of clear silicon sealer under the feet as I attached them to the roof. To eliminate the possibility of rust, I used stainless steel bolts, nuts, and washers to hold everything together.
I’m fortunate to have a south-facing roof on which to install my solar panels. Array mounting would be more complicated, and expensive, if my roof were east-west oriented. Shading from the array in the spring and summer helps to reduce heat in the attic. Notice in the photo that the panel's junction box is at the top, and therefore easily accessible.
An advantage to the steep winter configuration is that snow quickly falls off of the panels.
I'm confidant that this mounting structure will withstand high winds, and I've trimmed nearby trees to prevent damage from blowing and falling limbs. I should not experience shading from nearby trees execpt in the very early morning and again very late in the day. I look forward to the day when six more panels are added to this array.
Friday, February 09, 2007
Step 1. Determine your daily needs.
In order to keep energy needs low, look for ways to reduce power consumption. Replacing incandescent light bulbs with compact fluorescent bulbs is one way to do that. Electric clocks, doorbells, and certain other devices can be replaced by mechanical ones that do the same job. Once these things are done, you're ready to calculate your electricity needs.
A 13-watt compact fluorescent bulb for 5 hours = 13 times 5, or 65 watt hours.
A 25-watt laptop computer for 2 hours = 25 times 2, or 50 watt hours.
A 60-watt TV for 3 hours = 60 times 3, or 180 watt hours.
Total energy needs are found by adding up all of the loads, or in this case, 295 watt hours.
Step 2. Install enough solar panels to meet your energy needs.
If you get at least 3.5 hours of sunlight where you live, an 85-watt solar panel will give you 85 times 3.5, or 297.5 watts each sunny day. This exceeds your energy needs, but due to clouds and system inefficiencies, you're cutting it a little too close. You would be better off with a 100-watt panel or larger in this example.
For more information concerning the amount of sunlight you'll receive at your location, click here.
Step 3. Determine the size and type of batteries you'll need.
Batteries are rated in amp hours. Begin by converting watt hours to amp hours by dividing watt hours by 12 (the battery voltage). In this example, the 295 watt hours that you need divided by 12 equals 25 (rounded off), amp hours. Since we don't want to discharge the battery below 50% of it's capacity, we need a battery rated at no less than 50 amp hours. Because power needs are modest in this example, a department store Marine Deep-Cycle battery will do nicely. For a bigger system, I would recommend high-performance batteries instead.
Step 4. Select an inverter.
An inverter converts the 12-volts DC from your battery to 120-volts AC. To determine the size of the inverter needed, add up the power requirements of all of the loads that you intend to run simultaneously. The total of the loads in step 1 was just under 300 watts. Choose an inverter that is able to provide that amount of power continuously. For best results, choose a true sine wave inverter, not a modified sine wave inverter.
You can eliminate the inverter if you only want to provide power to 12-volt DC loads.
Step 5. Select a charge controller.
A charge controller efficiently controls the battery charging voltage and current, and keeps the batteries from overcharging. If you choose to build a single-panel system like the one described here, you need not get an expensive charge controller. A single panel can produce no more than 5 to 10 amperes of current, and just about any charge controller will be able to handle that. If you plan to add more panels to your system later, it would be wise to get a bigger charge controller up front, rather than replacing a small one later. You may choose to get a charge controller with additional features, such as a built-in meter, but expect to pay more.
The best charge controller will be the one that most efficiently charges your batteries, while using very little current for its operation.
Step 6. Additional considerations.
For system wiring, be sure to use wire that is large enough to handle the maximum current that will flow through it. Battery to inverter wires need to be heavy, since the current flow there can be very high. Solar panel to charge controller wire must be able to handle the 5 to 10 amperes of current that the panel produces in full sun, and therefore is not as thick as battery-to-inverter wire. Panels, as well as batteries, are connected in parallel for a 12-volt system. Keep in mind the fact that parallel devices double the current, but the voltage stays the same.
You'll also need at least one fuse or circuit breaker, and a lightning protection device. Make drawings, including a wiring diagram showing the size of each wire, before you begin.
By following these steps you can design a complete, off-grid, photovoltaic system. Take the time to explore battery options, as well as other system design details before starting. You'll find different brands of panels and equipment, and a wide range of prices as you shop. For additional details, check my previous blog posts and the websites listed below.
I'll be posting some how-to articles in the future, including instructions for building a simple solar panel mounting system using angle aluminum. So bookmark this blog and check back often.
As always, I look forward to your comments.
Thursday, February 08, 2007
Sadly, our federal government fails to recognize that springs flowing on Indian land have already run dry since Peabody Coal Company began using the water. Haven’t we done enough harm to Native Americans in this country? Does the need to supply coal to a power plant justify taking their drinking water and killing their fish?
More on this can be found here: http://www.biologicaldiversity.org/swcbd/press/black-mesa-02-06-2007.html
Can’t we just do the right thing? Support renewable energy projects.
Thursday, February 01, 2007
President Carter’s successor, Ronald Regan, should have supported the advancement of renewable energy technology, but instead he ripped out solar equipment that had been installed at the White House during the Carter administration. President Regan believed that drilling and mining was the way to prosperity.
The current administration, while claiming to be good stewards of the land, more closely follows the path of Ronald Regan than it does Jimmy Carter. The notion that conservation and renewable energy means giving up comfort still prevails. Fortunately, then as now, this simply is not true. We can be comfortable without burning fossil fuels and without harming the planet.
Just as you wouldn’t buy a two-seater car for a family of four, you shouldn’t settle for an undersized renewable energy system. If a solar photovoltaic system is properly designed, the user will not suffer through power shortages due to extended periods of cloud cover. Grid-tied systems simply use commercially available power when necessary. Switching back and forth is automatic. A properly sized system supplies more power than it uses over time.
For those who don’t mind a little extra work, a generator or windmill can be used to supplement energy from the PV system. To avoid burning fossil fuels, users may opt to fuel their generators with bio-diesel. In either case, the user doesn’t have to settle for shortages of electricity.
Another widely-accepted myth is that solar panels simply take up too much room to be practical. Those who accept this notion without questioning it are ignoring the obvious. Every home has a roof, and solar panels could be mounted on most of them. After all, A Roof is a Terrible Thing to Waste! (Sorry, I couldn’t resist saying that).
Additionally, it has been estimated that if a small portion of southwestern desert land was covered with solar panels, that single installation could meet the needs of the entire country. The desert southwest is an ideal location for a solar power site due to the amount of sunlight it gets, and because other uses for that land are limited. Distribution to distant parts of the United States presents a problem, but not enough to justify abandoning the idea. And the U. S. Department of Energy says "(Because of Dual Land Use), we wouldn't have to appropriate a single acre of new land to make PV our primary energy source." Notice that they said "primary" energy source. By making this statement they're saying that most coal, oil, and nuclear power generation facilities could be eliminated.
Sadly, those whose livelihoods depend upon the oil and coal industries don’t want you to know the truth about renewable energy alternatives, and well funded lobbyists pressure elected officials to support oil and coal interests. As a result, you’ll see misleading, and often inaccurate, articles regarding fossil fuel substitutes. I’ve found that I can save hundreds of dollars on my heating bill by supplementing my natural gas furnace with a corn-burning stove, but I doubt that the average person knows about that. I found out on my own, not from coworkers in the government office where I work, and not from the mainstream media. In addition, I’m starting to see savings as I add to my small photovoltaic system. As I continue my pursuit of renewable energy alternatives, I don’t intend to be uncomfortable or to give up anything. At the same time, I’m doing something good for the planet instead of polluting it.