Posted on April 7th, 2009 5 comments
I flipped the switch on the solar array today and watched my electric meter begin to run backwards, erasing not just today’s electricity usage, but most of yesterday’s as well. Today was a very sunny day in Colorado. These words were written on a computer that was, at the time of the writing, operating on solar energy alone.
For as long as I can recall, I’ve always wanted to own a house that ran on solar energy. My dad worked on the very first government communications satellites back in the 60’s and 70’s and he’d sometimes bring home bits and pieces of that project for my amusement. One of those early artifacts was a solar cell which is one of the technologies that allowed satellites to be practical in the first place. I remember being fascinated as I watched the solar cell power a small motor from a lamp. This was long before solar cells started showing up in calculators (which didn’t even exist at the time). The solar cells I played with back then are very similar to the ones that are now powering our entire house.
This solar installation uses a method called ‘net metering’, which feeds any excess electricity to the grid for use by my neighbors when the sun is shining. During this time, my meter runs backwards. After the sun goes down, my meter runs forward again. Based on the size of the array and our annual electricity usage, our house should have net zero electricity consumption over the course of the year. A net metering system has a few advantages over batteries because I don’t have to worry if we get several days with no sun, since I’m still hooked up to the grid. Also, a bank of batteries to hold just a day’s worth of electricity would be enormous, weighing over 2000 lbs. and they would also be costly. The savings from generating your own electricity are real, since for every kWh I generate, it means less coal or natural gas that needs to be burned back at the power plant.
I’ve always looked at the large south facing roof of our house as a perfect location for a solar array and now it’s here.
For those interested in specifics, the system includes 32 Sharp 176W panels connecting in 2 strings feeding a Sunny Boy inverter. Total capacity is 5.6 kW.
Posted on January 16th, 2009 No comments
I recently watched a series on the Discovery Science channel entitled Ecopolis. The premise behind each of the 6-part series was to showcase 4 promising technologies intended to solve the environmental problems of a hypothetical megacity of the future named, appropriately enough, Ecopolis. There were 5 episodes that each focused on a different issue, such as food production, transportation, energy, and waste disposal. In each episode, Dan Kammen, a Nobel prize winning scientist, would select the technology he thought held the most promise to solve the most critical issues that large cities face today and in the future. The 6th episode was a recap of the previous episodes and of the individual episode winners. Kammen also chose his overall favorite in the last episode.
The winner from the transportation episode was the eJeepney. The Jeepney, which is a portnamteau of Jeep and Jitney is used in the Philippines as a form of taxi-bus that carries about 16 passengers. It is a sort of cross between an Army Jeep and a Jitney. The original Jeepneys were built up from surplus Army Jeeps that the U.S. military had left in the Philippines after WWII. Subsequent models have been built on various Japanese vehicle frames usually in back lot operations, but the name ‘Jeepney’ remains. It’s an iconic vehicle of Philippine cities.
The eJeepney is an electric version of the Jeepney that was designed and built by Robert Puckett with the support of Greenpeace. These vehicles were designed from the ground up to be optimized for an electric motor drive. I was surprised to find that it used only a 5 HP (3.7 KW) motor and yet was able to carry as many as 17 passengers. Its top speed is 40 kph (26 mph). An 8-hour charge costs around 120 Philippine Pesos (PHP) and allows it to travel up to 120 km (75 miles). A PHP is worth about $US .0211, or just over 2 cents so 120 PHP comes out to around $2.50. An equivalent fill of diesel fuel, which is what most conventional Jeepneys require to travel a similar distance would cost about $6.50. The cost of riding a Jeepney is set at 8 PHP for the first 4 km (2.6 mi). This is about 17 cents. The e-Jeepney prototypes were built in China at a cost of around $8000 each.
The advantage of electric vehicles in congested cities can be significant. When an electric vehicle isn’t moving, it’s not using energy and even when it is moving, it is not polluting the air like the diesel powered Jeepneys. Considering there are 450,000 registered Jeepneys in the Philippines, the pollution caused by their diesel engines is a major health hazard.
I did some research and found that the price of electricity in the Philippines is about the same as the U.S. or $.010/kWh. So I can deduce that it takes about 25 kWh to charge an eJeepney. This is about the daily electricity use of an average U.S. household. Taking into consideration the inefficiencies of charging, I would estimate the batteries to be rated around 20 kWh. They are most likely to be lead acid which would weigh around 500 kg (1100 lbs) and cost in the neighborhood of $2000. The eJeepney has body panels made from fiberglass to save weight. One blogger mentioned that the eJeepney weighs 900 lbs. and I’m quite sure that is without the batteries. In looking at the heavy metal construction and ornaments on the traditional Jeepneys, weight savings were never an important consideration for these vehicles. Assuming that the passengers weigh about 150 lbs each, that mean the gross weight is about 4500 lbs, or about the empty weight of my Dodge Durango.
Accelerating a load of 4500 lbs with a 5 HP engine is likely to quite slow, and I’m not sure how it would get up a hill at gross weight, so my guess is that the routes would of necessity need to be quite level for these vehicles to make sense.
Another proposal related to these vehicles was to generate the electricity for them with organic waste converted to methane by anaerobic digesters, similar what’s happening in some landfills in the U.S. With the combination of the electric drive and electricity from a renewable fuel source, the benefits of the eJeepney gave it the nod for the overall winner of the Ecopolis series as well.
Sometimes people think that public transportation is the solution that all that ails modern society. There certainly are instances where taking public transit is more convenient than having to drive yourself. But I have to admit, like many Americans, I have a love affair with my personal vehicles. Public transportation is a hard sell once you’ve tasted the freedom and exhilaration of being in command of your own vehicle. Now, I’ll be the first to admit that a personal vehicle in a congested city is a major pain and I’m grateful for public transportation whenever I visit a bustling city, but when you’re located anywhere else on the planet, it’s hard to get along without one’s own personal ride. So while I can appreciate the eJeepney’s value in a huge metropolis, we don’t all live in cities, so I’d also like to see some more effort expended on making personal transport more environmentally friendly.
If you can get me one of these at a reasonable price, I’ll be very interested.
Posted on January 10th, 2009 5 comments
One of the frustrating aspects about renewable energy is that it is a highly technical field but it is followed passionately (and sometimes written about) by people who don’t know the difference between a watt, a BTU, a volt, or any of the mathematical and technical terms that are critical to understanding energy.
I was reading an article on LED lighting yesterday that had been mentioned in one of my LinkedIn groups and found that it used one of my pet peeves, mentioning CO2 reductions in the same sentence as energy savings. We should not care what the CO2 savings are when it comes to fossil fuels. All we need to know is that if the fossil fuel consumption is reduced by x%, then its CO2 output will be reduced by a similar percentage. Yet percentage saving are almost never mentioned. Some fossil fuels generate a little more CO2 per BTU than others, but it’s not important in the grand scheme of things. The important thing is that fossil fuels produce CO2 from carbon that has not been in the atmosphere for millions of years and that has the effect of increasing the atmospheric CO2 concentration when they are mined and burned. This is something we should try to avoid, because its consequences could be dire should it change the climate to make our planet inhospitable for humanity. Burning any carbon-containing fuel, including biomass like wood, alcohol, or biodiesel also produces similar amounts of carbon dioxide per unit of energy; it’s just that it is carbon dioxide that was recently in the atmosphere, not ancient carbon hidden under the earth’s crust, so it doesn’t increase the overall atmospheric CO2 concentration. And that is a vital distinction.
Most people have no idea how much a ton of CO2 really is. We don’t think of gases in terms of how much they weigh. Here’s a hint: If you’re an American, your fossil fuel per capita allocation is one ton of CO2 into the atmosphere approximately every 2 weeks. A ton sounds like a lot, but it’s not as big as you think when you consider that we each put 24 tons of CO2 into the atmosphere per year. Yes, we need to reduce it, and the only way to do that is by decreasing our overall fossil fuel consumption. OK, enough about ranting about my pet peeve, let’s get on to the LED lighting claims made by the article.
The article claimed that LED lighting would save $1.8 trillion, or 1 billion barrels of oil, and 10 gigatons of CO2 over 10 years. I wondered if anyone else bothered to do some simple calculations about these claims, like the fact that $1.8 trillion for 1 billion barrels of oil comes out to $1800/barrel, which is about 40 times its current price. Also, a barrel of oil weighs about 290 lbs, and burning a barrel of oil results in about 900 lbs of CO2. If you multiply a liquid fossil fuel’s weight by 3, it gives you a pretty accurate estimate of the amount of CO2 it generates when burned. Yet the conversion factor for the 10 gigatons for 1 billion barrels implies a yield of 10 tons of CO2 per barrel, or 20,000 lbs per 290 lbs of oil. This is off by more than a factor of 20.
It’s hard to imagine LED lighting saving so much money. For now I’ll ignore the fact that oil isn’t used very much for generating electricity. I’ll assume that the author was thinking in terms of “barrels of oil equivalent”. But the money savings don’t seem to hold up to scrutiny either.
I wrote an article on CFLs and my findings were that about 9% of electric energy usage in the home is due to lighting. CFLs can cut that by 75%, which means that their overall impact on home electricity use would generate around a 7% savings. That takes the lighting load down to about 2.3% of the total electrical load in a house.
Now that the low hanging fruit has already been eaten, LED lighting can only affect 2% of a typical electric bill. Although the article implies it can reduce that by a factor of 5, I think it would be at most half. I’ve found that LEDs are about 2 or 3 times more efficient in a lumens/watt metric than CFLs, not 5 times. Here are some typical luminous efficacy ratings of incandescents, CFLs, and LEDs from that article’s source:
Incandescent 16 lumens/watt CFL 64 lumens/watt LED 213 lumens/watt
A typical 60W incandescent bulb produces around 870 lumens of light. To get the equivalent amount of light, i.e., lumens, from LED bulbs it would cost over $100 compared to $1.50 for an equivalent CFL bulb. It would take a very long time to pay back that difference. A 60-watt equivalent CFL bulb uses about 13 watts, and using the more generous ratio given above (3.3), an equivalent set of LED bulbs would use 4 watts. This is a savings of 9 watts. Assuming a cost of $.10/kWh, it would take 110,000 hours or 12.5 years of continuous usage for the $100 of LED bulbs to break even with the CFL’s cost. Obviously, the cost of LED technology will need to come down significantly to make it competitive with CFLs.
LEDs have the benefit of using no mercury, unlike CFLs which do, but I covered the mercury issue in my CFL article so I won’t repeat it here. I also calculated the beneficial heat that is lost in the winter time when switching from incandescent bulbs. The extra heat generated by incandescent lights helps to reduce the furnace’s heating load, although not by much, just over 1%.
I think CFLs will be the heir apparent to incandescent bulbs for indoor applications for quite some time especially when you get above a hundred lumens. LEDs will reign supreme for battery powered applications where light output is less than 100 lumens and where the extra energy savings are vitally important. LEDs will also continue to find their way into applications where environmental ruggedness and long life are important.
Posted on December 19th, 2008 233 comments
I saw a two-page ad in the Rocky Mountain News this week about some new miracle heater called the ‘Amish Heat Surge‘ and it fell into the category of things that sounded to me to be ‘just a little fishy’. Later I saw a commercial for the same product. Sure enough, after doing some calculations, I figured out that this is just a scam to overcharge people for a cheap electric heater made in China. Searching the Internet, I found a few unhappy customers who fell for it. Even though the heaters are ‘free’, you pay $298 for the ‘Amish authentic wood mantles’ that enclose them. In reality, there’s no reason to wrap an electric heater with a wooden box or mantle. It also has some sort of fake fire effect. Oh, and shipping costs $50 EACH. And they’ll stick you with an extended warranty for $28 each. So for around $770, you’d get a pair of heaters that do the same thing as a pair of $27 electric heaters you can pick up at Wal-Mart.
A 5,119 BTU/hr heater generates about 1/20th the heat produced by a household furnace. It will draw 1.5 kW. For every hour this thing runs, it will cost about $.15 in electricity, which doesn’t sound like a lot, but over a 730 hour month, that adds up to an extra $108 on your electric bill. Electric resistive heat is the most expensive way to heat a house. It costs about twice as much per BTU as natural gas heat. Just to put it in another perspective, a 2,100 sq. ft. house in my home state of Colorado uses about 6 therms of natural gas a day in the coldest winter months. At the current gas price of $1.20 per therm, a typical gas bill is $216/month during the winter months. To heat your house to the same temperature with this electric heater, you’d need to have 5 of these heaters operating at the high setting 24 hours a day. The additional monthly charges on your electric bill for just the heaters would be $540!This heater can be yours for only $385This heater produces the same amount of heat and costs $27 at Walmart
The ad talks about only using it to heat zones, which can save on your heating bill, of course, but only at the expense of having some of the rooms in your home being uncomfortably chilly. And you can’t really completely turn off your central furnace without the risk of pipes freezing. In other words, if you put a heater like this in the room that has your furnace’s thermostat, and thus your furnace never comes on, you may freeze pipes in a remote part of the house.
The ad is full of high pressure sales nonsense, such as requiring a special savings code that expires in 48 hours, or you’d otherwise pay $587 each! There is a limit of 2 per household and they need to ‘turn away dealers’ because they can’t keep up with demand.
If you’re one of the people reading this article who bought an Amish Heat Surge heater, please note that I mean no disrespect to you. I’m just tired of con artists using slick advertising to suck people into buying things that aren’t worth a fraction of the sales price.