Posts Tagged ‘ Solar ’

Passive Solar Home Design

This was copied from here.
April 13, 2012 – 7:18pm
This North Carolina home gets most of its space heating from the passive solar design, but the solar thermal system (top of roof) supplies both domestic hot water and a secondary radiant floor heating system. | Photo courtesy of Jim Schmid Photography.<br />
This North Carolina home gets most of its space heating from the passive solar design, but the solar thermal system (top of roof) supplies both domestic hot water and a secondary radiant floor heating system. | Photo courtesy of Jim Schmid Photography.

What does this mean for me?

  • A passive solar home means a comfortable home that gets at least part of its heating, cooling, and lighting energy from the sun.

How does it work?

 Passive solar homes collect heat as the sun shines through south-facing windows and retain it in materials that store heat.

Passive solar design takes advantage of a building’s site, climate, and materials to minimize energy use. A well-designed passive solar home first reduces heating and cooling loads through energy-efficiency strategies and then meets those reduced loads in whole or part with solar energy. Because of the small heating loads of modern homes it is very important to avoid oversizing  south-facing  glass and ensure that south-facing glass is properly shaded to prevent overheating and increased cooling loads in the spring and fall.

Energy Efficiency First

Before you add solar features to your new home design or existing house, remember that energy efficiency is the most cost-effective strategy for reducing heating and cooling bills. Choose building professionals experienced in energy-efficient house design and construction and work with them to optimize your home’s energy efficiency. If you’re remodeling an existing home, the first step is to have a home energy audit to prioritize the most cost-effective energy efficiency improvements.

Site Selection

If you’re planning a new passive solar home, a portion of the south side of your house must have an unobstructed “view” of the sun. Consider possible future uses of the land to the south of your site—small trees become tall trees, and a future multi-story building can block your home’s access to the sun. In some areas, zoning or other land use regulations protect landowners’ solar access. If solar access isn’t protected in your region, look for a lot that is deep from north to south and place the house on the north end of the lot.

How a Passive Solar Home Design Works

In simple terms, a passive solar home collects heat as the sun shines through south-facing windows and retains it in materials that store heat, known as thermal mass. The share of the home’s heating load that the passive solar design can meet is called the passive solar fraction, and depends on the area of glazing and the amount of thermal mass. The ideal ratio of thermal mass to glazing varies by climate. Well-designed passive solar homes also provide daylight all year and comfort during the cooling season through the use of nighttime ventilation.

To be successful, a passive solar home design must include some basic elements that work together:

  • Properly oriented windows. Typically, windows or other devices that collect solar energy should face within 30 degrees of true south and should not be shaded during the heating season by other buildings or trees from 9 a.m. to 3 p.m. each day. During the spring, fall, and cooling season, the windows should be shaded to avoid overheating.
  • Thermal mass. Thermal mass in a passive solar home — commonly concrete, brick, stone, and tile — absorbs heat from sunlight during the heating season and absorbs heat from warm air in the house during the cooling season. Other thermal mass materials such as water and phase change products are more efficient at storing heat, but masonry has the advantage of doing double duty as a structural and/or finish material. In well-insulated homes in moderate climates, the thermal mass inherent in home furnishings and drywall may be sufficient, eliminating the need for additional thermal storage materials.
  • Distribution mechanisms. Solar heat is transferred from where it is collected and stored to different areas of the house by conduction, convection, and radiation. In some homes, small fans and blowers help distribute heat. Conduction occurs when heat moves between two objects that are in direct contact with each other, such as when a sun-heated floor warms your bare feet. Convection is heat transfer through a fluid such as air or water, and passive solar homes often use convection to move air from warmer areas — a sunspace, for example — into the rest of the house. Radiation is what you feel when you stand next to a wood stove or a sunny window and feel its warmth on your skin. Darker colors absorb more heat than lighter colors, and are a better choice for thermal mass in passive solar homes.
  • Control strategies. Properly sized roof overhangs can provide shade to vertical south windows during summer months. Other control approaches include electronic sensing devices, such as a differential thermostat that signals a fan to turn on; operable vents and dampers that allow or restrict heat flow; low-emissivity blinds; operable insulating shutters; and awnings.

Refining the Design

Although conceptually simple, a successful passive solar home requires that a number of details and variables come into balance. An experienced designer can use a computer model to simulate the details of a passive solar home in different configurations until the design fits the site as well as the owner’s budget, aesthetic preferences, and performance requirements.

Some of the elements the designer will consider include:

The designer will apply these elements using passive solar design techniques that include direct gain, indirect gain, and isolated gain.

Direct Gain

In a direct gain design, sunlight enters the house through south-facing windows and strikes masonry floors and/or walls, which absorb and store the solar heat. As the room cools during the night, the thermal mass releases heat into the house.

Some builders and homeowners use water-filled containers located inside the living space to absorb and store solar heat. Although water stores twice as much heat as masonry materials per cubic foot of volume, water thermal storage requires carefully designed structural support. An advantage of water thermal storage is that it can be installed in an existing home if the structure can support the weight.

Indirect Gain (Trombe Wall)

An indirect-gain passive solar home has its thermal storage between the south-facing windows and the living spaces. The most common indirect-gain approach is a Trombe wall.

The wall consists of an 8-inch to 16-inch thick masonry wall on the south side of a house. A single or double layer of glass mounted about one inch or less in front of the dark-colored wall absorbs solar heat, which is stored in the wall’s mass. The heat migrates through the wall and radiates into the living space. Heat travels through a masonry wall at an average rate of one hour per inch, so the heat absorbed on the outside of an 8-inch thick concrete wall at noon will enter the interior living space around 8 p.m.

Isolated Gain (Sunspaces)

The most common isolated-gain passive solar home design is a sunspace that can be closed off from the house with doors, windows, and other operable openings. Also known as a sunroom, solar room, or solarium, a sunspace can be included in a new home design or added to an existing home.

Sunspaces should not be confused with greenhouses, which are designed to grow plants. Sunspaces serve three main functions — they provide auxiliary heat, a sunny space to grow plants, and a pleasant living area. The design considerations for these three functions are very different, and accommodating all three functions requires compromises.

Passive Solar Home Design for Summer Comfort

Experienced passive solar home designers plan for summer comfort as well as winter heating.

In most climates, an overhang or other devices, such as awnings, shutters, and trellises will be necessary to block summer solar heat gain. Landscaping can also help keep your passive solar home comfortable during the cooling season.

External Resources
Crosbie, M.J., ed. (1997). The Passive Solar Design and Construction Handbook. New York: John Wiley &amp; Sons, Inc.
Kachadorian, J. (1997). The Passive Solar House. White River Jct., VT: Chelsea Green Publishing Co.
Van Dresser, P. (1996). Passive Solar House Basics. Santa Fe, NM: Ancient City Press.

Denmark Reaches 2020 Goal for Solar Energy

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Already this year, Denmark will reach the 2020 Government goal of 200 megawatt solar cell capacity.

Huge interest for solar energy solutions has made the amount of solar cells multiply much faster than expected. This is made possible by favourable framework conditions. In fact the solar cell capacity will be a hundred times bigger this year compared with 2010. Currently 36 MW capacity is being mounted every month.

Danish energy sector players, Dansk Energi, and DONG Energy, estimate that this development will result in 1000 MW by 2020 and 3400 MW by 2030.

Project Manager Kim Schultz from Invest in Denmark explains why the Danish market is booming:

“The demand for solar cells has increased dramatically since net metering was implemented in 2010. Net metering gives private households and public institutions the possibility of ‘storing’ surplus production in the public grid, which makes solar panels considerably more attractive.”

“Denmark benefits from a strong design tradition and this also characterizes the Danish solar sector in which aesthetics and thinking ahead of user needs is a central part of product development. This means that solar solutions are more likely to meet consumers’ demands.”

“Last but not least, Denmark has a unique energy system with a very high share of renewable energy. This makes the energy system very suitable as a platform for Smart Grid technologies, which are a key element to fully exploit renewable energy sources like solar panels and wind energy.”

A committed green market
Solar energy is only one element in a sound green strategy promoted by the Danish government. Denmark has a strong and broad political commitment to renewable energy, and earlier this year, the parliament entered into an ambitious agreement that will assure that 35 per cent of the Danish energy supply will be based on renewables by 2020, making it 100 per cent by 2050. Already today, Denmark covers 22 per cent of the national energy consumption with renewables.

“As part of the energy agreement, we are committed to creating a comprehensive strategy for establishing smart grids in Denmark. To promote the transition to renewable energy, we have furthermore dedicated 42 mio. DKK to analyzing how we can make green solutions like solar energy even more attractive in the future,” says Minister for Trade and Investment, Pia Olsen Dyhr.

As a result of the booming Danish market and Danish knowhow within smart grid and design, several foreign companies within the solar business have recently established in Denmark with the assistance of Invest in Denmark, among those Solarpark Rodenäs, Sunrider Solar and MHH Solartechnik.

For further information
Anne Lubbe, communications and online manager, Invest in Denmark, telephone: 3392 1378, e-mail:

How Solar Panels Work

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Solar panels work through what is called a photovoltaic process – where radiation energy (photo) is absorbed and generates electricity (voltaic).

Solar Panel Diagram: A cell level view of how solar panels work.This is called a photovoltaic process.

Radiation energy is absorbed by semi conductor cells – normally silicon – and transformed from photo energy (light) into voltaic (electrical current).

When the sun’s radiation hits a silicon atom, a photon of light energy is absorbed, ‘knocking off’ an electron.

These released electrons create an electric current.

The electric current then goes to an inverter, which converts the current from DC (direct current) to AC (alternating current).

The system is then connected to the mains power or electricity grid.

Crystalline Silicon Solar Panels

Traditional systems, called crystalline silicon solar modules, involve wafers of refined silicon beneath sheets of glass. The panels are surrounded by a metal frame.

A solar panel installer connects crystalline silicon panels – made with silicon wafers, glass panelling, and a frame.

These are by far the most common solar panels. If you’ve come across a solar panel installation, chances are it uses crystalline silicon technology.

Crystalline silicon technology has been used for around 50 years, and was first developed for powering satellites in space.

Current off the shelf crystalline silicon systems are generally capable of converting up to about 18 % of solar radiation exposure into useable electricity. This is termed as aphotovoltaic efficiency of 18%.

The main complaint of crystalline silicon is that the systems are expensive and bulky, installation requires a lot of wiring and labour, and that glass can be prone to damage.

Thin film solar panels

The new breed of solar technology is thin-film solar panels. Thin film is less bulky than crystalline silicon, and increasingly cheaper to produce.

New tech: Thin film solar panel cladding at the Solar Decathlon in Washington.

Thin-film solar energy systems currently have a lower photovoltaic efficiency than crystalline silicon – converting around 8% of radiation exposure – however the conductibility is expected to sharply rise as current research improves the method.

Thin-film solar panels work in the same photovoltaic manner as crystalline silicon modules, without the bulky wafers and glass panelling.

Amorphous silicon is a material usedin some thin-film flexible solar panels, which can be moulded to essentially any surface such as roofs or walls.

Rethinking How Solar Panels Work – New Methods and Applications

Solar research and development has boomed around the world over the last few years. These include new photovoltaic conversion methods and application technology, large scale solar farms, and increasingly efficient technology.

Below are a few of these developments.

Stirling Energy Systems’ California plant has developed a new solar electricity production method.

They use the sun’s radiation to heat hydrogen gas, which spins a generator, producing electricity. This method has a reported expected efficiency of 30%.

Another development is the number of large scale solar farms, which has recently spiked.

There are now 56 large scale (20 megawatt or more capacity) solar farms, with at least 27 more in the planning or development stages.

One of the largest, the Montalto di Castro Solar Park in Italy, produces 40,000 megawatt hours per year, enough electricity to power around 13,000 Italian households.

American company Solar Roadways has recently been awarded a grant by the US Federal Highway Administration to develop a solar car park.

The idea is to cover the car park’s surface in solar panels, creating a vast surface area for clean electricity production.

Solar Roadways co-founder Scott Brusaw envisages the project spreading to roads once the technology and methodology has been developed with the carpark project.

Beyond the possibility of turning whole roads into electric grids, other features in the pipeline include built in de-icing mechanisms and LED lighting for driver visibility, as well as recharging stations for electric cars – all using free solar energy.

Another US company, Dow Chemicals, have developed thin-film solar roof tiles.

The solar roof tiles are physically like any other roof tile, and are nailed to the roof just like traditional tiles.

How the tile solar panels work is along the same concept as conventional solar – the tiles plug into each other to create an array, then an electrician connects the panels to an inverter, and into the mains power of the building.

First all-carbon solar cell

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October 31, 2012 by Mark Shwartz

This shows the new all-carbon solar cell consists of a photoactive layer, which absorbs sunlight, sandwiched between two electrodes. Credit: Mark Shwartz / Stanford University (—Stanford University scientists have built the first solar cell made entirely of carbon, a promising alternative to the expensive materials used in photovoltaic devices today.

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The results are published in the Oct. 31 online edition of the journal ACS Nano. “Carbon has the potential to deliver high performance at a low cost,” said study senior author Zhenan Bao, a professor of chemical engineering at Stanford. “To the best of our knowledge, this is the first demonstration of a working solar cell that has all of the components made of carbon. This study builds on previous work done in our lab.” Unlike rigid silicon solar panels that adorn many rooftops, Stanford’s thin film prototype is made of carbon materials that can be coated from solution. “Perhaps in the future we can look at alternative markets where flexible carbon solar cells are coated on the surface of buildings, on windows or on cars to generate electricity,” Bao said. The coating technique also has the potential to reduce manufacturing costs, said Stanford graduate student Michael Vosgueritchian, co-lead author of the study with postdoctoral researcher Marc Ramuz. “Processing silicon-based solar cells requires a lot of steps,” Vosgueritchian explained. “But our entire device can be built using simple coating methods that don’t require expensive tools and machines.”

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Stanford Professor Zhenan Bao talks about the carbon solar cell research. Carbon nanomaterials The Bao group’s experimental solar cell consists of a photoactive layer, which absorbs sunlight, sandwiched between two electrodes. In a typical thin film solar cell, the electrodes are made of conductive metals and indium tin oxide (ITO). “Materials like indium are scarce and becoming more expensive as the demand for solar cells, touchscreen panels and other electronic devices grows,” Bao said. “Carbon, on the other hand, is low cost and Earth-abundant.” For the study, Bao and her colleagues replaced the silver and ITO used in conventional electrodes with graphene – sheets of carbon that are one atom thick –and single-walled carbon nanotubes that are 10,000 times narrower than a human hair. “Carbon nanotubes have extraordinary electrical conductivity and light-absorption properties,” Bao said.

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For the active layer, the scientists used material made of carbon nanotubes and “buckyballs” – soccer ball-shaped carbon molecules just one nanometer in diameter. The research team recently filed a patent for the entire device. “Every component in our solar cell, from top to bottom, is made of carbon materials,” Vosgueritchian said. “Other groups have reported making all-carbon solar cells, but they were referring to just the active layer in the middle, not the electrodes.” One drawback of the all-carbon prototype is that it primarily absorbs near-infrared wavelengths of light, contributing to a laboratory efficiency of less than 1 percent – much lower than commercially available solar cells. “We clearly have a long way to go on efficiency,” Bao said. “But with better materials and better processing techniques, we expect that the efficiency will go up quite dramatically.” Improving efficiency The Stanford team is looking at a variety of ways to improve efficiency. “Roughness can short-circuit the device and make it hard to collect the current,” Bao said. “We have to figure out how to make each layer very smooth by stacking the nanomaterials really well.” The researchers are also experimenting with carbon nanomaterials that can absorb more light in a broader range of wavelengths, including the visible spectrum. “Materials made of carbon are very robust,” Bao said. “They remain stable in air temperatures of nearly 1,100 degrees Fahrenheit.” The ability of carbon solar cells to out-perform conventional devices under extreme conditions could overcome the need for greater efficiency, according to Vosgueritchian. “We believe that all-carbon solar cells could be used in extreme environments, such as at high temperatures or at high physical stress,” he said. “But obviously we want the highest efficiency possible and are working on ways to improve our device.” “Photovoltaics will definitely be a very important source of power that we will tap into in the future,” Bao said. “We have a lot of available sunlight. We’ve got to figure out some way to use this natural resource that is given to us.” More information: Journal reference: ACS Nano search and more info website Provided by Stanford UniversityRead more at:

Experimental Direct Solar Steam Generation Power Plant Opens in Spain

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When most of us think of sunlight being used to generate power, we likely picture photovoltaic cells. Concentrated solar power plants however, use lenses or mirrors to heat fluid – such as synthetic oil – which in turn is used to generate high-pressure steam to drive a conventional turbine. A new experimental solar steam generation power plant that opened last week in southern Spain is aiming to improve on the efficiency of existing systems by using water as the direct working fluid and incorporating novel methods for storing the energy, so it can be dispensed even on cloudy days or at night.

The pilot plant is located in the municipality of Carboneras, and is the result of a collaboration between the German Aerospace Center (Deutsches Zentrum für Luft- und Raumfahrt, or DLR) and Spanish utility company Endesa. It was officially put into use on March 31st.

The water in the receiver tubes is kept at a pressure of up to 120 bar (1740 psi), which results in the creation of superheated 500C (932F) steam. That higher temperature allows the whole process to work more efficiently, bringing down the cost of solar thermal power generation and making it a more viable option.

Heat gathered by the plant can be stored in both sensible and latent forms, for use in creating energy when the sun isn’t brightly shining. In the sensible heat system, heat from the steam is absorbed by a concrete storage system, so it can later be released to create more steam and drive the turbine. In the latent heat system, the steam is used to heat salt, which absorbs energy when it reaches a temperature of 305C (581F) and changes from a solid to a liquid state. When the salt cools back down below 305 degrees and reverts to its solid form, that energy is released.

The Carboneras plant now boasts the world’s largest high-temperature latent heat storage facility.

“The advantage of such a system is its capacity to store large amounts of energy in a small volume and with a minimal temperature change,” said Doerte Laing, Thermal Energy Storage Research Area Manager at the DLR Institute of Technical Thermodynamics. “The energy in the system can be transferred and absorbed very efficiently by phase transition at a constant temperature.”

Researchers plan to keep the plant in use until the end of the year. They will be validating the direct solar steam generation process itself, the storage methods, and the flexible pipe connections that are necessary for the mirror and receiver tube assembly to pivot as it tracks the Sun.

Other articles by this author.

A Community in Canada Shares Solar

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A community in Canada has an unusual form of solar power that can provide over 90% of the annual heating and hot water needs for the homes, despite being situated in a cold Alberta location where winter temperatures can reach -33 degrees C (-27 F).

The Drake Landing Solar Community collects solar energy in a heat storage fluid through an array of solar panels on the roof of each home and covering all of the garages at the back of each home. The heated fluid is transferred to a neighborhood energy center, and then into the ground beneath an insulated layer, where the heat is stored in the earth.

Combined together, the 52 home community is able to collect and store enough energy from the sun during the summer that the ground storage temperatures reach 80 degrees C (176 F). This heat is sufficiently insulated beneath the ground that it can be drawn from throughout the winter to provide heat and hot water.

The homes in the community are moderately sized, ranging from 1,492 to 1,664 square feet, and are insulated to a level 30% higher than the average home in Canada in order to keep the energy needs low enough to work with the system. The homes are also closely located to one another. This provides a more walkable neighborhood, as well as reducing the lengths that the fluid for the solar heating system needs to travel.
Entire Neighborhood Has Shared Solar Heating

The system works in part due to the scale of the project utilizing the combined capacity of the entire community. A similar system scaled down to a single family home version would not work as efficiently simply because too much heat would be lost. But the scale of a system for 52 households makes this a feasible project.

Community heating system diagram

While the technology is similar to a ground source heat pump, which relies on a relatively stable, constant temperature of the ground, the Drake Landing Community is actually storing heat throughout the summer and then relying on that banked heat during the winter.

Solar heating is a more exciting prospect than solar generation of electricity because heating is a much larger percentage of a home’s total energy use (60% for space heating, 20% for water heating, and 20% for appliances, lights, and other electrical loads).

Green Building Elements (