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There are basically two key types of solar heating systems; solar passive and solar active.  Solar passive systems are typically less complex as they make use of solar energy without the need for additional electrical components and technology.  This typically makes them less costly but in many cases passive solar heating may not be effective for existing buildings if the current orientation of the building cannot take advantage of solar energy.  Solar active systems are a little more complex, although still relatively simple in comparison to some other environmental technologies, and are effective in both new and existing buildings.  Buildings don't have to use only one or the other.  It is certainly possible for a building to make use of both solar passive and solar active systems.  Let's take a quick look at the basics of both passive and active solar heating systems (even though you might not be thinking about heat today since it has been scorching hot outside this week).

Passive Solar Space Heating

Passive solar space heating takes advantage of the suns energy and warmth through features like large south facing windows and materials within the building that can absorb the suns energy in the form of heat during the day and release it at a later time.  These surfaces that collect this heat are often referred to as thermal mass, but we won't get into a big discussion on thermal mass right now other than to say they are a mass of some material that can effectively collect, and later release, thermal energy.

There are generally 3 design approaches used in Passive solar systems:

Direct gain - This is the simplest system.  It involves the collection of the suns energy in the form of heat by allowing the sun to shine directly on surfaces such as tile or concrete, directly within the room to be heated.  The surface absorbs the heat energy from the sun and later releases the heat into the room to help maintain the temperature.

In Part 1 of the Solar Pool Heating series we provided an overview of the basic operation of a solar pool heating system. In Part 2 we are now going to focus on why a Solar Pool Heating system might be a good choice for you.

Solar pool heating is a great way to get off of fossil fuels and save money while keeping your pool warm during the summer months. According to Natural Resources Canada the cost of a Solar Pool Heating system is very competitive with that of a natural gas heating system and may be even less than that of a heat pump based system. The average cost of a solar pool heating system is around $3000 (based on a 16ft x 32ft in-ground pool). Now if you consider you may pay a similar amount, or a little less, for a natural gas or electric system the benefits of a solar based pool heating system are many. Let's take a look at some of these benefits:

No Fuel Costs

Your solar pool heating system doesn't require any fuel for heating. Heat from the sun is transferred directly to your pool water as it circulates (typically using your existing pool pump) through the solar collectors on your roof. Energy from the sun is free. According to NRCAN data a typical 16ft x 32ft in-ground pool cost between $300 and $600 (using gas rate of ~$0.34 m³) to heat with natural gas each year (if you use a pool cover) with a heater efficiency rating of 68. If you don't use a pool cover your heating costs can almost double. A solar pool heating system would cost $0 in fuel if you don't need to supplement your pool heating during the season with natural gas. That's a potential savings of $3000-$6000 over 10 years just on fuel costs alone. If you need to replace an old existing system or are installing new it's certainly worth considering solar. In Canada, and particularly Ontario, many people might not realize it but we actually have some great solar energy potential. This graph from NRCAN shows the typical temperature for a solar heated pool in Ontario:

Solar pool heating systems are becoming more and more popular due to their simple design and since they are very cheap to operate as the suns energy is free.  In addition, since they don't use fossil fuels for heating and have a fairly long life expectancy due simple design.  In Part 1 of the Solar Pool Heating series we are going to discuss the basics of how these systems work. 

Open Loop Heating System

The simplest and most common system for seasonal pool heating or for heating in climates with high year round temperatures is an open loop system.  In an open loop system your pool water, as needed for heating, is pumped through unglazed solar panels where the suns energy, in the form of heat, is transferred to the pool water being pumped through the panel.  Below is a basic diagram of an open loop system.

There are many reasons that people choose to install Solar Domestic Hot Water systems today, one of them being the environmental benefits, but many people still wonder how much it will save them on their utility bills once it's up and running.  Although there is no magic way to come up with an exact number for everyone due to varying factors in each home let's take a quick look.  Based on some statistics available today we should be able to get a rough idea of the potential savings. 

 

According to statistics from Natural Resources Canada, on average, water heating represents about 20% of the energy use within a typical home. A lot of marketing material and articles in North America claim that water heating typically represents 20-30% and it will vary from home to home based on the technologies in your home as well as your water use patterns.

The general principle of how a thermal Solar Domestic Hot Water System works is relatively simple.  Energy from the sun is typically collected via glazed flat panels (solar) which transfer the sun's energy, in the form of heat to a mixture of distilled water and food-grade propylene glycol.  The mixture of propylene glycol with water is necessary to allow for year round application as it resists freezing. As the glycol fluid is heated by the sun's energy this heat is then transferred from the glycol mixture to heat the water in the solar hot water storage tank via a heat exchanger.  As hot water is used within the home the solar storage tank provides hot water to your existing main hot water heater instead of this water coming from your standard municipal cold water supply at temperatures around 10C.  The water in the solar storage tank has been pre-heated and may be hot enough that your hot water tank will not need to do any additional heating.  Even if the water from the solar hot water storage tank is not as hot as your main hot water heater setting, it may still be much warmer than the water temperature from your city/well water supply.  As a result, your hot water heater requires less energy to heat the water within the tank to the desired temperature and it can do it quicker.

Typically, SDHW systems are 2 tank solutions; 1) the solar hot water storage tank and 2) your existing main hot water tank. There are some single tank SDHW solutions that use solar to heat the water and have a backup electric heater for times where there is insufficient solar energy to heat the water to temperature, or maintain the desired temperature.  SDHW systems can also be used as a pre-heat for on-demand, or instantaneous, hot water heaters.

What is Passive Solar Energy

Passive solar energy is the concept of taking into consideration the effects of natural solar energy during building design to take advantage of daylight, space heating and/or space cooling.  It is called passive solar energy as it does not require special materials, technologies, or systems to convert the solar energy into electricity to then be used for heating, cooling or lighting.   The most common building component used in passive solar energy is windows. Over a year, most windows loose more energy than they gain. Advanced windows can actually be net energy suppliers, with better net annual energy performance than the most tightly insulated wall.For some hints and tips on effective use of energy efficient windows visit the Efficient Windows Collaborative organization.

Passive Solar Cooling   

Passive solar space cooling is used in warm climates around the world.  The key concept of solar cooling is to locate windows in the upper floor of a building so that this space is solar-heated during the warm season.  When the building requires cooling the windows are opened to allow fresh air in and hot air to escape.  By focusing the incoming air on lower levels of the building, or through air ducts in the ground, thus providing further cooling (using geothermal principles) cooler air is brought into the lower levels of the building, and hotter air escapes from the upper level.  Natural convection, or forced air can be used to increase the flow of the cooler air to upper levels of the building.

Passive Solar Daylight   

The basic concept of Passive Solar Daylight is very simple.  If you have sufficient natural light in your home during the day you don’t need to turn on lights, thus reducing the electricity used.Tips on taking advantage of passive solar daylighting can be found at the following link: US DOE Building Technologies Program.

Solar Collectors

Not only are there many different ways that solar energy can be applied, but there are also many different methods for collecting the solar energy from incident radiation.  Below is a listing of some of the more popular types of solar collectors.  

• Glazed flat-plate solar collectors
• Unglazed flat-plate solar collectors
• Unglazed perforated plate collectors
• Back-pass solar collectors
• Concentrating solar collectors
• Air based solar collectors
• Batch solar collectors
• Solar cookers
• Liquid-based solar collectors
• Parabolic dish systems
• Parabolic trough systems
• Power tower systems
• Stationary concentrating solar collectors
• Vacuum tube solar collectors

More information about collectors can be found at the  U.S. Department of Energy – Solar Energy Technologies Program: Solar Heating.                

Solar Power, A Quick Overview

Solar power is the transformation of the energy provided by sunlight into electricity.  The resulting electricity is known as Photovoltaic Energy.  Photovoltaic Energy is created through the conversion of sunlight via a photovoltaic (PV) cell, often referred to as a solar cell.  You have probably seen one on a calculator you've used in the past.

Sunlight is composed of photons, or particles of energy. The amount of energy in a photon corresponds to the different wavelengths of the solar spectrum.  Available solar energy is often expressed in units of energy per time per unit area, such as watts per square metre  (W/m²). The amount of energy available from the sun outside the Earth’s atmosphere is approximately 1367 W/m²; that’s nearly the same as a high power hair drier for every square meter of sunlight!  Some of the solar energy is absorbed as it passes through the Earth’s atmosphere.  As a result, on a clear day the amount of solar energy available at the Earth’s surface in the direction of the sun is typically 1000 W/m².  At any particular time, the available solar energy is primarily dependent upon how high the sun is in the sky and current cloud conditions.  On a monthly or annual basis, the amount of solar energy available also depends upon the location.  Furthermore, usable solar energy is depends upon available solar energy, other weather conditions, the technology used, and the application.  When photons strike a photovoltaic cell, they are either reflected, absorbed or pass right through the cell. Photons that are absorbed by the cell are able to provide energy to generate electricity. When enough sunlight (energy) is absorbed by the material (a semiconductor), electrons are excited and "freed" from the material's atoms.  The exciting of electrons, resulting in a bouncing back and forth, creates friction and therefore heat. The solar cell takes a percentage of these electrons and directs them to flow in a path. This flow of electrons is, by definition, electricity.