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5. Efficiency and low-waste strategies in the lower right column.

Tuesday, July 20, 2010

How to turn Global Warming into an Asset

Tuesday, January 29, 2008

Energy Island: unlocking the potential of the ocean as a renewable power source

Energy Island sketch
Image Gallery (5 images)

January 29, 2008 While governments and corporations were exploring petroleum as a fuel source in the 19th century, Jacques Arsene d’Arsonval proposed another liquid source for power – the ocean. It may have taken a hundred years, but his ideas are finally starting to come into fruition. Ocean Thermal Energy Conversion uses the temperature difference between surface and deep-sea water to generate electricity – and though it has an efficiency of just 1-3% - researchers believe an OTEC power plant could deliver up to 250MW of clean power, equivalent to one eighth of a large nuclear power plant, or one quarter of an average fossil fuel power plant. Architect and engineer Dominic Michaelis and his son Alex, along with Trevor Cooper-Chadwick of Southampton University are developing the concept with plans of putting the theory to the test on an unprecedented scale by building a floating, hexagonal Energy Island that will harness energy from OTEC, as well as from winds, sea currents, waves, and the sun.

The US National Renewal Energy Laboratory estimates that the world’s tropical seas absorb the solar power equivalent of 250 billion barrels of oil per day. OTEC uses warm surface water to vaporize a fluid with a low boiling point, typically ammonia or propane, and pumps cooler water from depths of up to 1000 meters below the surface to re condense the fluid. The movement of the liquid through the system is enough to continually power a turbo-generator. The simplistic nature of the station, which behaves almost like a gigantic internal combustion engine, allows OTEC power plants to be largely self-sufficient. And unlike wind and solar energy, which have a fluctuating output that changes according to the weather and the time of day, the regularity of ocean temperatures and movements provide a far more stable and consistent source of power.

The Energy Island project is bidding for the US$25 million funding offered by Richard Branson’s Virgin Earth Prize, which is awarded for environmentally responsible research. The OTEC technology is something of a green dream; not only is it clean and renewable, but so are its by-products. By subjecting the steam to electrolysis, large quantities of hydrogen can be produced, paving the way for cheaper hydrogen fuel cells. And by using an Open-cycle OTEC - where low-pressure containers boil seawater and condense the steam elsewhere after passing it through the turbo-generator – large amounts of fresh water can be created. Energy Island is also packed to the brim with other renewable energy collectors, with wind, wave, current and solar sources providing a total of 73.75 MW.

Michaelis estimates it would take a chain of 4-8 Energy Islands to achieve the production levels of a nuclear power plant. To replace nuclear power entirely, Michaelis estimates a chain of 3708 modules would be required, stretched over a total length of 1928 kilometres, and consuming a total square area of roughly 30 by 30 kilometres. To shoulder the entire global energy consumption, based on 2000 figures, 52 971 Energy Islands would be needed, occupying a total area of 111 x 111 kilometres - described on the Energy Island site as “a pin point in the oceans.” Though the Islands have to be spread out to be effective, their location doesn’t infringe on otherwise usable real estate, as is the case with land power stations, and some bioethanol farms. Michaelis claims that in certain areas, chains of Energy Islands may even help maintain the environment, by combating erosion from the predicted rising sea levels, supporting deep-water ecosystems and aquaculture, and cooling greenhouses.

Energy Island isn’t the first project to portray OTEC as the solution to Earth’s power and pollution woes. Previous plans for the technology, most notably John Craven’s, have been positively utopic. Craven saw OTEC not only as a source of cheap power and water, but also as a method for accelerating crop growth, and, (no utopia would be complete without it), a provider of free air conditioning. Project Windfall, meanwhile, was a plan authored by a Florida group that involved installing an OTEC plant in order to reduce the hurricanes that routinely ravage the east coast.

But while OTEC has captured the imagination of scientists, it has not had nearly so much success with governments. The United States established the Natural Energy Laboratory of Hawaii Authority in 1974, viewing the high electricity costs of the state, and the dynamics of the surrounding water, as the ideal testing ground for OTEC technology. The NEL successfully demonstrated a 250 kW closed-cycle plant in 1999, but ultimately the money evaporated faster than the water, and Congress shifted attention to more economical areas of research. OTEC could be commercially viable, said test director Luis Vega, but it needed “patient funding” to reach that stage.

Only now, with rising oil prices and the increasingly cataclysmic predictions of global warming, could OTEC receive the “patient funding” necessary for progress. Plans for OTEC plants are being entertained by the governments of Japan, Taiwan, India, South Africa, the Philippines and the US, which recently passed a bill that gives OTEC, and tidal, wave, and ocean current research, $50 million per year for five years.

However, the next breakthrough in OTEC research may well come from the armed forces. The US government has been directing its various departments into funding and using renewable energy – in an example that must give Democrats migraines of confusion, Guantanamo Bay receives a quarter of its power from wind energy. By 2025, the Pentagon is to increase its renewable energy use to 25% of its total power. The Navy is planning to build an 8MW OTEC facility in 2009, near the island of Diego Garcia in the Indian Ocean, while the Army is planning to build an OTEC facility in the Marshall Islands in the Pacific.

As the Energy Island site states, despite being 100 years old, OTEC is in its infancy. But given the renewed interest, and the multitude of various benefits, it’s possible that the next 100 years of this concept could profoundly change the energy and environmental management of the Earth.

Wednesday, July 14, 2010

Conservation and Efficiency First Steps to Solar

Inflate This: Conservation and Efficiency Are Key to Our Energy Future

Of the recent political maneuvering and verbal attacks in the current presidential election, perhaps one of the most disappointing and frustrating has been John McCain's disparagement of conservation and efficiency. Mocking Obama's call for Americans to make sure their tires are properly inflated to help reduce gasoline consumption: The McCain team started handing out tire gauges to journalists and editors engraved with the words: "Obama's Energy Plan."

Give me a break!

It's time that serious and informed policymakers stop putting down one of the most effective energy sources of all: conservation and efficiency (or what some people call the "fifth fuel.") There's nothing funny about disparaging one of our most valuable energy assets. It's common knowledge among energy experts that the lowest hanging fruit is often conservation and efficiency. And I believe that most traditional "conservatives" in the mold of Theodore Roosevelt and British statesman Edmund Burke (often credited with founding modern conservatism) understand the value of energy "conservation."

Conservation and efficiency also make good economic sense. In some research my colleagues and I recently conducted at Clean Edge, we analyzed the capital costs to deploy a range of energy generation and energy reduction measures for utilities. In most cases, energy conservation efforts (everything from implementing energy efficiency programs to demand side management) came in as the least expensive option.

On the automobile front, the Department of Energy estimates that "you can improve your gas mileage by around 3.3 percent by keeping your tires inflated to the proper pressure." Combined with regular tune-ups, replacing clogged air filters, and using the right oil grade, the U.S. Department of Energy estimates that the average driver could save 18-19 percent combined. So how much savings are we talking about? According to the U.S. Government Accountability Office, about 1.2 billion gallons of fuel per year could be saved from properly inflated tires alone (equal to about one percent of total gasoline consumption).

And many of these conservation measures can be done in very short order.

By contrast, opening up drilling in areas that are currently off-limits in the Gulf of Mexico and off the Atlantic and Pacific Coasts of the lower 48 states are estimated to be just slightly more than the savings that could be achieved via proper tire pressure. The Energy Information Administration projects that there's about 1.5 billion gallons of gasoline a year that could be accessed from new offshore drilling, but that it wouldn't come online for years. To be fair, some industry estimates show that this number could be much higher, but no clear metrics exist.

Amory Lovins and Hunter Lovins, in their 1998 Club of Rome report Factor Four: Doubling Wealth, Halving Resource Use, outlined how to do just that: double the world's wealth while cutting the use of our resources in half. They wrote in the book's introduction: "‘Factor Four,' in a nutshell, means that resource productivity can — and should — grow fourfold. The amount of wealth extracted from one unit of natural resources can quadruple. heralds nothing less than a new direction for technological ‘progress.'"

These remain awfully sage words in today's carbon- and resource-constrained world.

But in his attempt to score political points by painting Obama in some cardigan-wearing, Carteresque light — McCain did a disservice to the broader energy dialogue. It harkens back to Vice President Cheney's discounting of energy efficiency more than seven years ago, when he stated "Conservation may be a sign of personal virtue, but it is not a sufficient basis for a sound, comprehensive energy policy."

The future of energy in the U.S. will involve a combination of many different technologies, policies and business approaches. There is no one silver bullet. In my estimation, we're talking about the massive scale up of solar, wind and other non-hydro clean-energy sources (getting to 30 percent of the nation's electricity generation by around 2030); the extensive build-out of green buildings and energy-sipping built environments; the deployment of a smart grid and plug-in hybrid and all-electric vehicles; and yes, energy efficiency measures as simple as tuning one's car and weatherizing one's house for the winter.

The issues we face will require an integrated, whole-systems approach that utilizes the best weapons in our clean-energy arsenal. In fact, a review of both Obama's and McCain's web sites, point to a range of options and policy recommendations by both candidates. Implying otherwise is simply ludicrous.

And, I believe, near the center of any 21st Century energy plan should sit a robust energy efficiency and conservation component — one that is exemplified rather than belittled.

Ron Pernick is co-founder and managing director of Clean Edge, Inc., coauthor of The Clean Tech Revolution, and Sustainability Fellow at Portland State University's School of Business.

Comments on article:
Actually, what is even harder to understand than brain-dead politicians like Cheney and McCain, is why individuals who can easily afford it don't simply start upgrading their equipment to the most efficient available including cars, housing, and appliances. The return on investment is way better than the stock market in most cases and will only get better as energy prices increase. Could it be that no-brainism is contagious?

Dump those gas guzzlers. Get those efficient refrigerators, laundry appliances and triple glazed windows. They will never again be cheaper than they are now (because inflation and currency devaluation never stop).

My guess is that if everyone in the U.S. who could afford to do so, would take these steps, we could reduce our energy use by 15-25% and the investment would be repaid in reduced operating costs within 2-7 years. So let's stop "Dicking" around (sounds so much better than 'Cheney-ing' around) and save ourselves and our children from a collapse of the biological foundations of life. That is a no-brainer.

Micro-Inverters are the best solution

September 8, 2008

Time for a Change: Micro-inverters Improve Performance of Solar Systems

by Raghu Belur, Enphase Energy

There are many challenges in current solar technology. These challenges include the inefficiencies in photon-to-electron conversion, system reliability, and the difficulties in installing and managing solar installations. The majority of current research and development funding is looking to address the first issue by focusing on improvements in solar module technology and manufacturing. While this is important to drive down the cost of solar modules, there are additional opportunities for improvement in solar system performance. Re-thinking the role inverters can play in solar installations is one way to address the challenges associated with energy harvest, reliability and management of solar systems.

Traditional Inverters

Inverters perform two key functions — converting the DC power from the solar modules into grid quality AC power and performing Maximum Power Point Tracking (MPPT) on the solar array. MPPT is the algorithm that extracts the maximum amount of power from the solar array.

Traditional centralized inverters manage all the solar modules in an array as an aggregate — a single source of energy. But there are limitations in using a single MPPT for multiple solar modules. Non-uniform changes in temperature, irradiance and shading create complex heterogeneous current-voltage curves, making it difficult for an MPPT algorithm to operate efficiently. This can result in the conversion of less than the maximum power available from the solar modules. An associated issue is that a traditional inverter represents a single point of failure in the solar system. A final limitation of traditional inverters includes noise pollution, space constraints and aesthetic issues. The larger the solar power system, the larger the inverter that is required, sometimes requiring a separate facility that must be constructed, powered, cooled and maintained.

The Micro-inverter Systems Approach

The idea of a micro-inverter has existed for many years — using multiple small inverters instead of a large, centralized inverter to distribute the power conversion of a solar installation. Early designs met with limited success because they failed to achieve the efficiency, reliability and price point required to achieve regulatory and commercial viability. More recent designs such as one from from Enphase have taken these lessons to heart, and micro-inverters are being developed and tested to meet the industry regulations and customer requirements. What is emerging is a micro-inverter that produces more energy, is more reliable and less expensive to install and maintain than traditional inverters.

Harvest Gains, Reliability, Design and Installation

Micro-inverter technology offers significant technological advances. The first is per-module MPPT, which ensures energy harvest is maximized. With traditional inverters, the performance of the entire array is degraded if one or more modules becomes dusty, covered in debris or shaded. Micro-inverters enable each module to perform independently within the solar array. This benefits the system owner by maximizing energy harvest since degraded performance from one solar module will not prevent the rest of the modules from producing their maximum energy. The per-module micro-inverter also eliminates the problem of reduced energy harvest due to module mismatch. Tests have shown an increase in energy harvest in the order of 5 to 25%.

As with the migration from a central mainframe to personal computers in the information technology industry, the distributed nature of the micro-inverter system significantly alters the landscape of the solar industry. A centralized inverter failure in a traditional design renders the entire solar array useless until a replacement can be ordered and installed. With a micro-inverter approach, a single inverter failure only affects the module to which it's attached, and contributes to an insignificant degradation in total system output. This means that micro-inverters can be replaced at the convenience of the installer or during a regularly scheduled maintenance visit. In addition, no specialized personnel, equipment or tools are required to replace a micro-inverter. This distributed approach can achieve system availability of greater than 99.8 percent — a key factor for commercial systems.

The micro-inverter approach also promises to increase design flexibility and lower installation costs. Micro-inverters are connected in AC branch circuits eliminating the need for expensive DC combiner boxes, disconnects etc. This means that installers no longer have to deal with restrictions of string design or with the headache of locating and installing a large traditional inverter. Individual solar modules no longer have to be "matched" because each module is an independent energy producer with its own MPPT. Use of micro-inverters eliminates the hassle of working around varying module ratings and standardizes the installation process. The per-module inverter approach means that installers have the flexibility to install solar modules on any available roof surface without the restriction of coplanarity.

Enphase Energy has extended the concept of a micro-inverter into a complete system, which includes the micro-inverter, embedded powerline communications and Enlighten — a web-based performance monitoring and analysis tool. The tool is able to compare modules and if it notices an energy harvest issue, it uses built-in algorithms to analyze the cause of the issue and whether the owner or installer needs to be notified.

With a systems approach to solar generation that delivers greater productivity, higher reliability and smart management, micro-inverter systems significantly improve the performance of solar systems.

Raghu Belur is a co-founder and vice president of marketing at Enphase Energy Inc. He has 15 years of experience in engineering and engineering management. He began his career at the Indian Institute of Science where he worked on a team developing an alternative energy gasification system. He was an early engineer at Cerent Corporation where he was responsible for the development of the optical 2.5Gig interface for the Cerent-454 ADM. Cerent was acquired by Cisco Systems in 1999. At Cisco, Raghu was managing the team developing the 10Gig interface products. He co-founded Enphase Energy Inc in March of 2006. Raghu has a MSEE from Texas A&M University.


From Jonathan Cole:

Excellent, Raghu! I have been trying to promote this approach for decades. Finally it is getting done. Another incredible advantage to this approach is longevity. Small inverters (and charge controllers) at 90%+ efficiency dissipate hardly any heat because the load of the entire array is distributed into such small packets. This means the long-term heating issues that degrade components in larger inverters are no longer an issue. It means that passive heat dissipation such as radiative cooling and micro heat pumps are viable instead of having to rely on fan driven systems which are a point of failure in a system made to last 15 years or more. This amounts to longer life and lower cost.

Since such mini inverter modules can be plugged into the back of a solar panel, much as you might plug a nightlight into a receptacle, replacement takes minutes. This then means that advanced technology upgrades are viable which is important over the life of a solar electric system since it may be as log as 40 or 50 years.

I have a friend who has been operating a 300 watt inverter continuously for 15 years without a failure. Packaging all components into individual panels is the way to go. Now when we include energy storage such as the lithium titanate batteries being offered by Altairnano, we come up with the ultimate self charging uninterruptible power supply. Take it to mass production, and the energy problem is on its way to being solved.

Comments From Ben Gatti

Spreading the heat components around, makes it more expensive to manage the heat not less. When the heat is close, you can use fans, heat-sinks, and temperature sensors to control heat, with active heat control, one can use the full capacity of the components.

If many large inverters where more cost effective than larger ones, there would be no market and a negative price curve for larger inverters. In Fact, inverters at the high end of the power continuum are about half the cost per watt as those at the low end.

Having serviced residential and commercial low-voltage systems in the past, I am somewhat skeptical of the savings long-term. A single point of failure can be very easy to diagnose; while finding a problem somewhere on a high, hot, and sloped roof, at the end of a long ladder, is more dangerous and more expensive.

On flat commercial roofs, you can get away with equipment spaghetti, but on a sloped roof; I would prefer as little as possible up there, and as much as possible mounted in a cool place at eye level, but that's the been-there-done-that part of me talking.

I do like the idea of better MPPT efficiency, and fully scalable systems; But micro-inverters will need to be fully integrated into the Panel before the pros outweigh the cons.

Reply from Jonathan Cole:

Ben, You clearly have not looked at the instrumentation demo on EnPhase's website. With this advance in instrumentation there is no longer any diagnosis necessary. You know what you need too fix before you even go up on the roof. And while economies of scale may now favor large inverters, that is only because all of these products are not yet in the true realm of advanced automated mass production. When these things are being manufactured in the hundreds of millions of units, I guarantee you that they will be dirt cheap

Ben, I think you may be misinterpreting the way such a system would work. It is true that with a single inverter you would not have to go up on the roof. On the other hand with the micro-inverter system, with each panel putting out AC and running in parallel, if one fails, you won't need to go on the roof until a convenient time. Because even if 15% of your panels fail, you are not out of business. But with a single inverter, failure is a complete power outage. Since small inverters will be more reliable because they don't have mechanical heat dissipation, there should be much less need for repair. The ideal is to have inverters that can last the life of the PV and even to be economically upgradable, since electronic technology continues to improve over the 30-50 year life of the PV.

When the inverter and charge controller are integrated with the panels it means that a single AC wire can come from the entire array which seems like much fewer connections and much less wire cost to me. And the data for the instrumentation can be multiplexed on the electrical signal so that no additional wiring is required for complete AC/DC instrumentation.

As far as connecting batteries into such a system, they are connected between the charge controller and the inverter, just as in every un-integrated independent system - like the one I have been living on for 26 years. I am sure that EnPhase is probably targeting the grid-tied market, but it is only a relatively small step to integrate storage when the economic issues are supportive.

Cheaper per watt has to include the maintenance and installation costs, including wiring, and enclosures for weather protection, etc. Even in Hawaii we have these costs and they are significant. We need an integrated product that can be installed in a morning and supply sophisticated data reports, querying, alarms and instrumentation to have user-friendly, 30-50 year installations with high reliability.

This awaits visionary investors.

Comment From Ben Gatti:

I appreciate your points - I do, But I think you've failed to make the case for three key points:

1. That a transistor sitting on a roof will run cooler than in the moderate temperatures of a shaded garage. Try this experiment, park your car in a garage, then park it in the hot sun; use the vinyl seat test or some other scientific method. Trust me that roof is a hotter environment.

2. A Single failure won't cause a problem. This I think is a maybe. Ever had a Mosfet fail? It shorts. Not sure what would happen if a few Mosfets short over; maybe not much. But saying doesn't make it so.

3. How do you include batteries in a one-panel, one inverter system? If I understand you correctly, You'd have batteries behind each panel, connected between the "Charge Controller" and the inverter. That would mean climbing the roof to replace the batteries. Now you have to admit that's a bit of a tricky wicket.

Reply from Jonathan Cole:

Actually the development of panel mounted inverters already goes back quite a way. The first that I heard of was an Australian firm. They did not have the right design and went under. Lately, Exceltech has come out with this product on the market.

Before you get too sure that this is a bad idea, you might want to look a little closer. Actually underneath a PV panel remains remarkably cool. One quarter inch from the back of my Kyocera panels in Hawaii on a full-sun summer day at noon (we have very strong sun), it is the same as ambient temperature. If you put your hand back there it does not feel any warmer than the air. Most of the heat dissipated from most solar panels rises (because heat rises) and does not come out the back of the panel. This is why here in Hawaii, large hotels are covering there roof with PV, because they generate electricity and lower their cooling costs at the same time. PV on a roof is a heat interceptor and dissipates nearly all of it upward. As far as being able to put a battery pack back there as well, you might want to check out

Integrated PV/electronics/storage is the future in my opinion. The fact is, that without storage there is a limit to how much time-variant solar energy can be utilized by the grid. Of course it might put a lot of old style installers out of business, but only if they refuse to see the writing on the wall, because once these products are in mass production, the demand will be enormous. So it might only take a few hours for the installation of the entire system, but there will be millions of systems to install instead of tens of thousands.

Don't forget that 100 years ago, every automobile was a custom, one of a kind integration of a hodgepodge of parts. Mass production is what changed things and it will be no different with integrated PV/electronics/storage systems

Solar Breakthrough

Solar Power Game-Changer: 'Near Perfect' Absorption Of Sunlight, From All Angles

ScienceDaily (Nov. 4, 2008) — Researchers at Rensselaer Polytechnic Institute have discovered and demonstrated a new method for overcoming two major hurdles facing solar energy. By developing a new antireflective coating that boosts the amount of sunlight captured by solar panels and allows those panels to absorb the entire solar spectrum from nearly any angle, the research team has moved academia and industry closer to realizing high-efficiency, cost-effective solar power.

“To get maximum efficiency when converting solar power into electricity, you want a solar panel that can absorb nearly every single photon of light, regardless of the sun’s position in the sky,” said Shawn-Yu Lin, professor of physics at Rensselaer and a member of the university’s Future Chips Constellation, who led the research project. “Our new antireflective coating makes this possible.”

An untreated silicon solar cell only absorbs 67.4 percent of sunlight shone upon it — meaning that nearly one-third of that sunlight is reflected away and thus unharvestable. From an economic and efficiency perspective, this unharvested light is wasted potential and a major barrier hampering the proliferation and widespread adoption of solar power.

After a silicon surface was treated with Lin’s new nanoengineered reflective coating, however, the material absorbed 96.21 percent of sunlight shone upon it — meaning that only 3.79 percent of the sunlight was reflected and unharvested. This huge gain in absorption was consistent across the entire spectrum of sunlight, from UV to visible light and infrared, and moves solar power a significant step forward toward economic viability.

Lin’s new coating also successfully tackles the tricky challenge of angles.

Most surfaces and coatings are designed to absorb light — i.e., be antireflective — and transmit light — i.e., allow the light to pass through it — from a specific range of angles. Eyeglass lenses, for example, will absorb and transmit quite a bit of light from a light source directly in front of them, but those same lenses would absorb and transmit considerably less light if the light source were off to the side or on the wearer’s periphery.

This same is true of conventional solar panels, which is why some industrial solar arrays are mechanized to slowly move throughout the day so their panels are perfectly aligned with the sun’s position in the sky. Without this automated movement, the panels would not be optimally positioned and would therefore absorb less sunlight. The tradeoff for this increased efficiency, however, is the energy needed to power the automation system, the cost of upkeeping this system, and the possibility of errors or misalignment.

Lin’s discovery could antiquate these automated solar arrays, as his antireflective coating absorbs sunlight evenly and equally from all angles. This means that a stationary solar panel treated with the coating would absorb 96.21 percent of sunlight no matter the position of the sun in the sky. So along with significantly better absorption of sunlight, Lin’s discovery could also enable a new generation of stationary, more cost-efficient solar arrays.

“At the beginning of the project, we asked ‘would it be possible to create a single antireflective structure that can work from all angles?’ Then we attacked the problem from a fundamental perspective, tested and fine-tuned our theory, and created a working device,” Lin said. Rensselaer physics graduate student Mei-Ling Kuo played a key role in the investigations.

Typical antireflective coatings are engineered to transmit light of one particular wavelength. Lin’s new coating stacks seven of these layers, one on top of the other, in such a way that each layer enhances the antireflective properties of the layer below it. These additional layers also help to “bend” the flow of sunlight to an angle that augments the coating’s antireflective properties. This means that each layer not only transmits sunlight, it also helps to capture any light that may have otherwise been reflected off of the layers below it.

The seven layers, each with a height of 50 nanometers to 100 nanometers, are made up of silicon dioxide and titanium dioxide nanorods positioned at an oblique angle — each layer looks and functions similar to a dense forest where sunlight is “captured” between the trees. The nanorods were attached to a silicon substrate via chemical vapor disposition, and Lin said the new coating can be affixed to nearly any photovoltaic materials for use in solar cells, including III-V multi-junction and cadmium telluride.

Along with Lin and Kuo, co-authors of the paper include E. Fred Schubert, Wellfleet Senior Constellation Professor of Future Chips at Rensselaer; Research Assistant Professor Jong Kyu Kim; physics graduate student David Poxson; and electrical engineering graduate student Frank Mont.

Funding for the project was provided by the U.S. Department of Energy’s Office of Basic Energy Sciences, as well as the U.S. Air Force Office of Scientific Research.

The Problem With Concentrated Solar Power (CSP)

The problem with all forms of CSP is that any clouds interfering with direct sunlight causes there to be effectively zero energy conversion, since CSP requires a point source of light like the sun on a clear day. The scattered light available when there is any type of cloud cover comes from many directions and cannot be focused. Such cloud cover can linger for days or even months. On the other hand, flat plate photovoltaic and thermal collectors create useful energy conversion even on a cloudy day. The useful energy conversion in these simple systems is proportional to the light, and do not require direct sunlight nor mechanical tracking with its substantial costs and maintenance issues. With climate change altering cloud cover in many areas, CSP is a risky investment.

Jonathan Cole

Cheap, Energy-efficient Refrigeration

Energy Efficient Refrigeration Solutions
by Scott Middlekauff edited by Jonathan Cole

I used to be among the hordes of off-the-grid homeowners in search of an affordable method of keeping my food cold. My ice chest was affordable, but little else. My tiny propane fridge cost $800, required frequent trips to town for fuel, cost over $200 per year for propane, and it was depressing to be buying fossil fuels. I longed for a Sunfrost, which is efficient, but costs more than my car. Finally, my regular upright fridge tripled my total energy usage. The defrost cycle alone in this an “energy star” fridge used 450 watt/hours per day. 450 watt/hours just to heat my fridge! To top it off, every time I opened it all the cold air spilled out onto my feet. Mine used over double what it was rated, using about 2400 watt/hours per day.

[I decided to edit this and add stuff that is appropriate to current conditions and possibilities and remove obsolete stuff. The stuff I added is in blue. Jonathan Cole]

At long last, I think I have discovered the cheapest and most energy efficient refrigeration system. My method costs a bit over $300, and uses about 350 watt/hours of electricity per day. This could run on the equivalent of one 75 watt solar panel.

Basically, I just hooked up a regular chest freezer to a cheap appliance timer.
Use a Heavy Duty Timer made by Woods, Model 59377, available at Ace Hardware for about $25.
First, I will assume that you already have an electrical system with an inverter. I don’t know what size inverter that you need to account for the surge, but the compressor uses about 100 watts once it’s running. I would guess that a 600 watt inverter would be plenty of capacity for the surge. [Use a minimum of 1100 watts, true sine wave inverter. Refrigeration compressors momentarily surge up to ten times their continuous run rating.]

I bought a regular 8.8 cubic foot chest freezer. You could get a bigger one, but I wouldn’t recommend any smaller, because the relative energy efficiency is a bit lower. Then I got a “heavy duty” plug-in appliance timer for $13, a couple of large Tupperware containers, and a piece of stiff mesh metal screening (a piece of plywood with holes drilled in it would work fine). A digital thermometer is optional.

The timer needs to be a type with at least three on settings and three off. I chose to set my timer to cycle on for one hour at 9am, one hour at noon, and one hour and a half at 3 pm. The reason for this time schedule is to have the compressor running during times when the sun would normally be shining, so that there will be no strain on the batteries. I also chose to spread out the “on” times as much as possible, so that the fridge doesn’t actually get frozen in the middle of the day, or warm up too much during the night. The compressor cools off the fridge pretty fast, so you wouldn’t want it to be on for much longer than one and a half hours all at once, or else some foods will get a bit frozen.

Get a stainless steel refrigerator/freezer thermometer. I have one made by EKCO and bought at the supermarket. The thermometer is to check the temperature in the fridge during the first couple of weeks and adjust the total number of on hours on the timer to get the exact temperature that you want. I feel personally happy with 36-40 degrees. Below 34 risks freezing. At mid 40′s food spoils too fast for me. Based on your personal use, you may need to have your compressor running more, or less, than 3 1/2 hours per day. Our ambient temperature is around 75 degrees.

The stiff metal screening and the tupperware containers have two functions; thermal mass to keep the fridge cool all night, and to raise the bottom of the freezer box so that it is more convenient for people to use. You see, the bottom of the freezer is two different levels; there is a step where the compressor is housed. The result is that most of the freezer box is over 30 inches deep. This is fine for occasional access of typical freezer users, but too awkward for daily usage. So, what I did was fill two large tupperware containers with water (for thermal mass), and place them in the low part of the freezer. To even out the surface so that the entire freezer bottom is at the same level, I placed the stiff metal screening to create a shelf, on top of the two tupperwares. The result is a fridge of about 7 cubic feet, with about 70 pounds of water at the bottom.

If you need the entire 8.8 cubic feet of space, and you want to devise other ways of utilizing the bottom part of the fridge, try it out and let me know how it goes. I would forget about the food way down there, but with properly marked stacked containers, an orderly person could surely have success.

When you first start up the fridge, you will have to leave it on for several extra hours at first, in order to cool off the 70 pounds of water. That’s all. Your fridge is ready to go.

Warning: Don’t insulate a chest freezer. Unlike most refrigerators, the cooling and heat dissipating coils are located all over the walls of the freezer box, so if you add insulation, you will prevent the compressor from getting rid of the heat. The compressor and the food inside will heat up. When the freezer is running, you can verify this by putting your hand on the outside of the freezer; it’s quite warm. An exception on our freezer is the lid. There are no heating or cooling coils on the door. So, actually, I could glue some foam sheeting to the lid with beneficial results. My friend Ann keeps a blanket on top of her freezer.

As an alternative to the "freezer converted to refrigerator" If you want to get an 18 cubic foot fridge like mine it can be ordered at Home Depot for about $650 and takes about 5 weeks to get it. GE Mode l# GTH18EBC2RWW. On a timer for 12 hours a day (8 AM - 8 PM) it uses on average 600 wattHrs a day. The freezer contents stay frozen and the food in the fridge stays cold and does not spoil. The advantage of it is that you have both a spacious freezer and a fridge. I love mine. Jonathan Cole