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Passive water heater diagram
Thermosiphoning is considered to be an appropriate technology. This process utilizes natural, renewable resources and the basic laws of thermodynamics to create movement of a heated supply of air or water. The energy source for this process is solar radiation: the energy of the sun is captured in a solar collection device and is transferred to either air or water via conduction. The entire process may be explained by the thermosiphoning effect: When air or water is heated, it gains kinetic energy from the heating source and becomes excited. As a result, the water becomes less dense, expands, and thus rises. In contrast, when water or air is cooled, energy is extracted from the molecules and the water becomes less active. It also becomes more dense, and tends to "sink." Thermosiphoning harnesses the natural density differences between cold and hot fluids, and controls them in a system that produces natural fluid movement.

The passive thermosiphoning of water is the process of heating and moving water within a system without the need or use of electricity. This process functions by utilizing natual phenomena such as solar energy, gravity, and an available water source. A solar collector, piping, and a water tank are materials required for the heating process. The flow of water is distributed into, within, and out of the solar collector. Cool water enters the bottom of the solar collector where it is then heated via convection by solar radiation. When water is heated it becomes less dense than cooler water, expands, and then rises (flows) through the piping. The heated water exits the top of the solar collector naturally. The cooler and more dense water sinks and remains within the solar collector until it is heated. As the cool water is heated, it expands, rises, is pushed out of the top of solar collector, allowing cool water to flow into the solar collector. This process continues naturally until the temperature of the water reaches an equilibrium with solar radiation input.

...Archive/Nominations

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Portal:Solar/Selected page/1

Solar cell
Photovoltaics. Every day across the globe, the sun shines down on the earth. The energy in the photons from the sun can be converted to electrical energy. The term for this process is the "Photovoltaic Effect."

Since the first commercially available solar panel in the 1960´s, photovoltaic (PV) technology has continued to be explored and developed throughout the world. The constant development of this technology has resulted in an increasing level of efficiency and PV panels that are more affordable than ever before, though still initially expensive. Today, humans continue to search for new ways to make photovoltaic technology a viable option for everyone throughout the world. Since most of us are not studying the atomic level of this technology, we can help in other ways - by gaining an understanding and spreading that understanding of photovoltaics, as well as by helping others to gain access to solar, or photovoltaic, systems.

Photovoltaic technology holds a number of unique advantages over conventional power-generating technologies. PV systems can be designed for a variety of applications and operational requirements, and can be used for either centralized or distributed power generation. PV systems have no moving parts, are modular, easily expandable and even transportable in some cases. Sunlight is free, and no noise or pollution is created from operating PV systems. PV panels do not require the use of fossil fuels such as coal, oil or natural gas in the energy production process. Alternatively, conventional fuel sources have created an array of environmental problems, namely global warming, acid rain, smog, water pollution, rapidly filling waste disposal sites, destruction of habitat from oil spills, and the loss of natural resources.

...Archive/Nominations

Portal:Solar/Selected page/2

Solar heater
Solar hot water describes active and passive solar technologies that utilize the sun’s freely abundant solar thermal energy in order to heat water for a desired application. It is one of the most efficient ways to heat water (in terms of energy/waste), as it requires no energy conversion, unlike electric-resistance heating or fuel burning. It is a simple transfer and concentration of heat energy from one place to another. Another interpretation of the efficiency of the practice is that the solar energy is free, and only dependent on the extent of the technology used, and its cost and efficiency. In other words, the energy is free, only the collection, conversion, and storage devices cost.

If you have ever felt hot water trickle out of a garden hose that’s been sitting in the sun, you’ve experienced solar hot water in action. Essentially, a solar hot water system is made up of a solar thermal collector, a well-insulated storage container, and a system for transferring the heat from the collector to the container vis-à-vis a fluid medium, which in some circumstances is the water to be used itself.

Being as there are, on a global scale, near countless applications using domestic, commercial and industrial hot water, there are also nearly as many opportunities to apply solar thermal technologies to heat this water. But today the market is changing, and both the economic and environmental costs associated with using gas and electricity to heat water are being challenged by more efficient, less costly systems.

...Archive/Nominations

Portal:Solar/Selected page/3

The finished greenhouse!
Construction of an Affordable Greenhouse. The capstone project for Queen’s University 4th Year Mechanical Engineering Class,"Engineering for Sustainable Development", is to design and construct an Appropriate Technology with a quantifiable engineering result. This project is to construct a greenhouse, review the heat requirement on the system for the whole year; then, based on the materials and conditions selected, review costs associated with this and build a scaled model.

This project is the first step to easy community greenhouse development - the goal of the affordable greenhouse is to:

  1. Improve greenhose design and awareness for residential application.
  2. Demonstrate the feasibility (i.e costs) of a greenhouse in the winter months and determine the best time to install such a system for optimal crop yield.

Due to the materials selected and the cold Canadian Spring, it is not effective to construct until late April. But with better material selection and innovative greenhouse designs, it is hoped that constructing miniature greenhouses will become common practice.

The blueprints for the construction of an affordable greenhouse are included; for this greenhouse a single pane Polyinyl chloride (PVC) covered greenhouse was reviewed. Heat losses and calculations were done in MatLab using constants from the Canadian Climate Normals website and sunlight radiation from Queen's University Living Building.

-Happy growing!

...Archive/Nominations

Portal:Solar/Selected page/4

Passive water heater diagram
Thermosiphoning is considered to be an appropriate technology. This process utilizes natural, renewable resources and the basic laws of thermodynamics to create movement of a heated supply of air or water. The energy source for this process is solar radiation: the energy of the sun is captured in a solar collection device and is transferred to either air or water via conduction. The entire process may be explained by the thermosiphoning effect: When air or water is heated, it gains kinetic energy from the heating source and becomes excited. As a result, the water becomes less dense, expands, and thus rises. In contrast, when water or air is cooled, energy is extracted from the molecules and the water becomes less active. It also becomes more dense, and tends to "sink." Thermosiphoning harnesses the natural density differences between cold and hot fluids, and controls them in a system that produces natural fluid movement.

The passive thermosiphoning of water is the process of heating and moving water within a system without the need or use of electricity. This process functions by utilizing natual phenomena such as solar energy, gravity, and an available water source. A solar collector, piping, and a water tank are materials required for the heating process. The flow of water is distributed into, within, and out of the solar collector. Cool water enters the bottom of the solar collector where it is then heated via convection by solar radiation. When water is heated it becomes less dense than cooler water, expands, and then rises (flows) through the piping. The heated water exits the top of the solar collector naturally. The cooler and more dense water sinks and remains within the solar collector until it is heated. As the cool water is heated, it expands, rises, is pushed out of the top of solar collector, allowing cool water to flow into the solar collector. This process continues naturally until the temperature of the water reaches an equilibrium with solar radiation input.

...Archive/Nominations

Portal:Solar/Selected page/5

Earth bound radiation losses
The solar resource. Solar energy is the source of all energy on earth, available to us in a number of derivatives. Plant matter for example, which relies on solar energy for nutrition, experiences natural compression and decomposition over millions of years to form the the fossil fuels we use today for electrical generation and transportation. Other examples of this can be seen in use of biomass for fuel or the harvesting of wind energy which is reliant on solar heated air for the formation of currents.

We are also able to utilize the solar resource directly. Solar thermal technologies take advantage of this resource to heat a working fluid that can transfer energy to an air stream or water for domestic or commercial use. Solar Photovoltaic or PV devices exploit various materials (principally Silicon) that experience sub-atomic variations when exposed to solar energy in order to induce an electric current. Both solar PV and thermal technologies provide a useful source of energy with little to no moving parts, no pollution and very little embodied energy.

In order to effectively design a solar energy system, an understanding of the available solar resource at the location of interest is required. All of the energy available on Earth is derived from the sun. We can model the sun's surface as blackbody. At a specific temperature, approximately 5777K for the sun, a blackbody emits energy with a unique radiation spectrum. The spectrum is divided into three broad ranges classified as ultraviolet, visible and infrared which transmit radiation at varying intensities. The highest intensities are found within the visible spectrum, peaking at a wavelength close to 0.5um. Averaged over the entire surface, the power density of the sun is found to be approximately 63 x 10 W/m2.

...Archive/Nominations

Portal:Solar/Selected page/6

Direct and diffuse solar radiation (Practical Action)
Solar thermal energy. The sun is the source of the vast majority of the energy we use on earth. Most of the energy we use has undergone various transformations before it is finally utilized, but it is also possible to tap this source of solar energy as it arrives on the earth’s surface.

There are many applications for the direct use of solar thermal energy, space heating and cooling, water heating, crop drying and solar cooking. It is a technology which is well understood and widely used in many countries throughout the world. Most solar thermal technologies have been in existence in one form or another for centuries and have a well-established manufacturing base in most sun-rich developed countries.

The most common use for solar thermal technology is for domestic water heating. Hundreds of thousands of domestic hot water systems are in use throughout the world, especially in areas such as the Mediterranean and Australia where there is high solar insolation (the total energy per unit area received from the sun). As world oil prices vary, it is a technology which is rapidly gaining acceptance as an energy saving measure in both domestic and commercial water heating applications. Presently, domestic water heaters are usually only found amongst wealthier sections of the community in developing countries.

Other technologies exist which take advantage of the free energy provided by the sun. Water heating technologies are usually referred to as active solar technologies, whereas other technologies, such as space heating or cooling, which passively absorb the energy of the sun and have no moving components, are referred to as passive solar technologies.

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