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Created by Torben Brosten, last modified by Benjamin Brink 18 Aug 2010, at 09:47 AM
Solar technologies are getting their day in the sun in Ontario, and the companies behind them are basking in the rays.
It's been a long time coming. Until recently, the wind industry has received most of the support in this country as the premier renewable-energy option, coming in the form of policies, incentives or private investment.
Solar has been the poor cousin, always there and supportive of wind, always mentioned alongside other renewables, always the sexy headline-grabber, but lacking any lobby power and rarely taken seriously in political circles as an alternative energy worth backing with funds.
That began to change last year, at least in Ontario, after the province began accepting applications for its standard offer program, which pays 42 cents for every kilowatt-hour of clean electricity that comes from small solar projects...
read full article at: http://www.thestar.com/article/228987
Created by Torben Brosten, last modified by Benjamin Brink 18 Aug 2010, at 09:44 AM
[This report describes a marketing strategy] ..to use as a template for solar manufacturers, builders, energy service providers, or other interested businesses. The marketing plan contains a brief summary of the background and current status of the industry for solar water heaters, an outline of potential opportunities in the building industry, and defines the marketing strategy including defining the product, distribution channel, pricing strategy and promotional mix.
Document at: http://www.osti.gov/bridge/servlets/purl/12184-Qg25WS/12184.PDF
Created by Torben Brosten, last modified by Benjamin Brink 18 Aug 2010, at 09:28 AM
Created by Torben Brosten, last modified by Torben Brosten 28 Jul 2010, at 11:31 PM
Created by Benjamin Brink, last modified by Benjamin Brink 05 Jul 2010, at 06:04 AM
Closed loop systems use heat-exchangers that circulate heat-transfer fluids through the panels and feed pipes. This type of system is called a closed-loop system, because the solar exchange fluid is closed-off from the external atmosphere or isolated from the potable water through utilization of a heat exchanger.
A closed-loop system works essentially by heating solar fluid that is pumped through the solar collectors. The heated solar fluid flows through a copper or stainless steel heat exchanger located near the solar storage tank. The heat from the solar fluid transfers to the potable water within the solar storage tank. Another small circulator pump may be used to circulate the water through the potable side of the heat exchanger.
strengths
The anti-freeze heat exchange fluids can withstand freezing temperatures, allowing the system to operate during periods when there is the greatest temperature difference between cold incoming water, and temperatures reached in the solar collectors. The system can have the greatest performance benefits at this time. Also, if maintained properly, these systems will not corrode or scale the passage ways in the solar collectors and pipes. Closed-loop systems tend to have the lowest overall operating costs --other than passive systems-- and are especially adapted to work in regions with extended periods of freezing temperatures, and commercial environments that are used daily (including weekends).
A closed-loop system is a good alternative to consider if installation conditions inhibit installing a drainback system, for example because the feed and return pipes to the solar panels cannot be plumbed at an adequate slope (usually 0.25inch per 1 horizontal foot or steeper).
weaknesses
Closed-loop systems tend to have the highest installation cost associated with them. They heat water slightly less efficiently than direct open-loop systems, (but can work more and longer when it is risky to operate open-loop systems). These systems are designed to operate daily, and may overheat (releasing heat transfer fluid) if the fluid in the closed-loop does not circulate during a hot summer day --for example, when a unit is shutoff because residents leave for vacation. At these times, instructions sometimes call for panels to be covered to prevent discharges due to overheating.
Closed-loop water heating systems in the catalog
DekkaSupply.com > Solar and Radiant Hydronic Heating > Closed-Loop systems and modules
Created by Benjamin Brink, last modified by Benjamin Brink 05 Jul 2010, at 06:00 AM
Open loop systems directly heat potable water. Open-loop systems work essentially by circulating water through the solar collectors via a small pump mounted on a water storage tank. The solar pump is activated by a differential thermostat controller that senses when heat is available in the solar collectors. The solar storage tank connects to the existing hot water heater and feeds the preheated solar water into the gas or electric hot water heater as hot water is used.
In regions where pipes can freeze, the solar collectors and feed lines are usually protected from freezing by automatic drain down controls. These Drain down systems allow the water in the pipes and panels to fall safely back out of the solar collectors and feed pipes to prevent freezing. These types of systems are "open loop" since the energy collection loop is not separate from the rest of the hot water system --i.e. the loop is "open" and sharing the same water.
strengths
Regular maintenance costs are associated less with open-loop systems because they don't use any special fluids or heat exchangers used with closed-loop systems. They are usually cheaper to install than closed-loop systems. Open-loop systems are more efficient at heating water than closed-loop systems, because water is directly heated from the solar panels.
weaknesses
The main weakness is related to the Drain-Down portion of these systems. An open-loop systems' "drain down" freeze protection can fail, subjecting system owners to risk of substantial repair costs from freeze damage and property damage such as flooding from broken pipes. These costs can significantly outweigh the benefits of using this kind of system. A system drained-down for protection purposes can miss some of the best opportunities for providing high-performance benefits of solar hot water heating. Open-loop systems are vulnerable to early component deterioration when operating with hard water.
Open-loop water heating systems in the catalog
DekkaSupply.com > Solar and Radiant Hydronic Heating > Open-Loop systems and modules
Created by Benjamin Brink, last modified by Benjamin Brink 05 Jul 2010, at 05:56 AM
Thermosiphon systems are a kind of passive solar water heating that use some of the passive components of active systems, such as flat plate solar collectors. The solar panels usually are mounted at a lower elevation than the storage water to be heated. Thermosiphon systems can circulate potable water or utilize a heat exchanger and heat exchange fluid.
For potable water systems, the cooler water at the bottom of the storage tank is thermally siphoned to the hotter water near the solar collector by the raising temperature and volume of the warmer water, initiating a circulation of the storage water through the collectors fluid passage ways back into the top of the storage tank. The circulation continues until the temperature at the bottom of the storage tank is about the same
as the temperature of the outlet pipe at the top the solar collector.
Thermosiphon systems using a heat exchanger work on the same principle by circulating a nonfreezing solar exchange fluid through an internal heat exchanger installed inside the solar storage tank, instead of circulating potable water. This type of system is usually installed in climates that experience freezing temperatures to prevent freeze damage of the solar collectors and siphon pipes.
strengths
Thermosiphon systems, like other passive solar systems, usually cost less
than active solar systems to purchase and maintain.
weaknesses
Regardless of the thermosiphon system used, care needs to be taken that the water feed pipes connecting the solar collectors to the water heater inside the house or building do not freeze. Insulation of the feed pipes does not guarantee against freezing. We recommend a manual drain down of the pipes and tank preceding freezing conditions. Also, thermosiphon systems need special installation conditions not associated with the active solar systems. Open-loop thermosiphon systems do not work well with hard water.
Created by Benjamin Brink, last modified by Benjamin Brink 05 Jul 2010, at 05:38 AM
background
On average, 13% to 26% (17% overall) of energy in a US household is consumed heating water[1].
Heating water using conventional sources of heat contributes significantly to a household's utility bill and green-house-gas (GHG) emissions[2].
Solar water-heating systems significantly reduce the amount of utility power consumed in the process of heating water.
Using solar power to heat water significantly reduces GHG emmisions and saves water heating costs. The more water is heated by the sun, the less conventional energy is used to heat water.
system designs 
Heating water by the sun can be as simple as painting a bucket black and leaving it in the sun.
Solar water heating systems work on the same basic principle and consist primarily of these designs:
There are many variants that accomplish the same result. These may use parabolic troughs, concentrating mirrors, freon or oils as a heat transfer fluid, and vacuum tubes etc.
The majority of solar hot water heating systems installed in the United States are highlighted above. Their popularity is due to cost efficiency and proven performance over decades of use.
1 - according to the US Energy Information Administration (EIA) data.
2 - extrapolated from EIA data with GHG and co2e equivalents from The Climate Trust.
Created by Benjamin Brink, last modified by Benjamin Brink 05 Jul 2010, at 05:34 AM
experiential explanation of passive solar water heating
A simple way to passively heat water with the sun:
- paint a container or bucket black,
- pour water into it,
- put it out in the sunlight,
- wait a few hours..
..presto! Free hot water, compliments of Ra, the ancient Egyptian Sun
God. The bucket system is a "passive" system because it does not use any moving parts or electricity.
scientific explanation
Photons radiating from the sun reach the bucket's surface and are absorbed by molecules at the surface. As molecules absorb light, the energy is converted to angular momentum --making the molecules move and rotate faster. We observe the faster motion as an increase in heat. Heat travels as the energy in the motion is transfered to other nearby molecules as molecules bounce into each other --faster molecules tend to transfer some of their energy to their slower (cooler) neighbors. In this way, some of the heat from the bucket travels to the water. The transfer of heat is called thermal conduction and obeys the laws of thermodynamics[1] including the law of conservation of energy[2], not to be confused with human-legislated conservation laws[3]. For more on this, follow these links:
hot water from the sun
We enjoy hot water for washing hot showers and loosening grit and grime from our skin, clothes, dishes, floors and pets, and increasing ambient temperature in a home, shelter, pool or spa. Heat from the sun is heat from nature. There is an emotional warming component of solar heat not found with heat generated from alternate sources and ultimately indirect solar.
batch collectors
Passive "Batch" collectors are a more sophisticated form of the bucket example. The collectors are coated with a dark, absorbent surface. Each collector consists of an insulated metal box, covered with a solar glass or glazing material, and containing a tank of sorts that is larger than a bucket and holds water. Usually batch collectors are filled with pressurized water.
strengths
Batch collectors operate without the need of "active" pumps or controls, so
they don't need much maintenance. Also, because they don't have any automatically moving parts, they can be the least expensive system to purchase, build, and maintain.
weaknesses
Batch collectors are not as efficient as "active" collector systems. Also, batch collectors should be installed only where freezing is not a problem, because the water pipes that feed the batch collectors (and the storage tanks) are prone to freeze damage. Owner participation is usually required to prevent freeze damage, by manually draining the batch collector during near freezing weather conditions. Draining the water can be awkward, because water weighs about 8 pounds a gallon, and collectors usually have a capacity over 50 gallons each. A 50 gallon collector's water would weigh over 400 pounds.
Passive water heating systems in the catalog
DekkaSupply.com > Solar and Radiant Hydronic Heating > Passive systems and modules
Further reading
http://en.wikipedia.org/wiki/Solar_water_heating#Passive_systems
Created by Benjamin Brink, last modified by Benjamin Brink 05 Jul 2010, at 05:33 AM
Active solar heating systems use parts that have motion ("active"). Active systems are more complicated than passive system designs,
but are increasingly easier to operate and maintain, because manual maintenance tasks are replaced with automatic ones. From the simplicity of the black painted
bucket method of passive systems, engineers long ago developed active systems to accelerate heating and retain stored heat for convenient use.
Flat plate solar collectors
Highly efficient "flat plate" solar collectors are at the heart of active solar water heating systems, converting sunlight to heat energy. They are usually made out of a set of
parallel copper pipes ("riser tubes" or "risers") that are
embedded or soldered onto a thin copper "fin" (3) that runs the length of the riser
tubes (4). The "fins" increase the absorption of the solar rays, transferring more
heat into the water or various kinds of heat-transfer fluids that can be circulated
through the riser tubes. The riser tubes and fin assembly are brazed into 2
horizontal "header" pipes at the bottom (7) and the top (2) of the riser tubes. The
solar absorber plate is then installed in an aluminum framed box (6) surrounded on
the bottom and sides with insulation (5) and covered with tempered glass (1).
Flat plate solar collectors ("solar panels") are a key component
in active solar systems. The collector plates have a constant flow of fluid through them when heating.
Three basic designs identify active solar water-heating systems:
There are variations, but they accomplish the same result usually resembling one of these when distilled to their basic design.
The hybrid drainback systems are popular as these systems use the best of both closed-loop and open-loop designs, and manufacturers have continued to improve on the design and components over the years.
