PacB Group // Residential Solar Solutions

Articles

Residential Solar Solutions

Photovoltaic and Thermal Solar Power Solutions for Residential Use

Radiant energy from the sun is hot enough to melt lead both on its nearest planetary neighbour, mercury, and on Venus, more than 30 million miles further away. After travelling another 30 million miles or so, its radiant energy level drops to a point where it has proved just perfect to initiate and to sustain life on our home planet – Earth. It does so by promoting plant growth and photosynthesis that provide food and oxygen for animal respiration, consuming exhaled carbon dioxide during the hours of darkness. Inhabited by sentient beings for just 200 000 of its 4,5 billion-year lifespan, humankind has recently harnessed solar radiation to provide energy solutions for residential, commercial, and industrial applications.

For such purposes, the sun’s rays may be utilised in one of two ways, employing either their thermal or their photovoltaic effects. The first of these employs the physical principles of thermodynamics known as radiation and conduction. Heat from the sun takes the form of infrared rays, which reach the earth and penetrate its atmosphere by the process of radiation. Upon striking the surface of a suitable object, that heat will be absorbed by conduction, thus raising the temperature of that object. This is the principle employed by a system designed to generate hot water from the heat of the sun, and forms the basis of the simpler of the two residential solar solutions referred to earlier.

Consisting of a collector, hot water tank, heat exchanger, pump, and control system, the first of these components is responsible for collecting the radiant energy. It consists either of fluid-filled copper pipes encased beneath black glass to maximise absorption, or evacuated tubes that relay their heat to a separate fluid-filled manifold. In each case, the heated fluid is pumped through a copper coil immersed in the hot water tank. This acts as a heat exchanger, heating the contents of the tank while returning the cooled fluid in the coil to the collector where it can then be re-heated. A basic controller for thermal residential solar solutions might simply operate a switch to turn the pump on or off, while a more sophisticated model could include facilities, such as temperature and pressure gauges, flowmeters, and thermostats. The system can be integrated with a conventional immersion heater, switching between power sources as required.

While still reliant upon both radiation and conduction, in addition to these thermodynamic properties, a photovoltaic system also employs some clever chemistry, utilising the captured radiant energy, not to heat water, but to generate an electric current. The advantages of this technology are clear. When in the form of electricity, this energy obtained from the sun can be used for a much wider range of purposes. Though somewhat more expensive, the photovoltaic option is by far the more versatile of these two residential solar solutions.

Acting as a combined collector and converter, each large panel consists of an array of individual photovoltaic (PV) cells, each composed of two layers of semiconducting material. The upper layer is electron-rich and acts as an emitter, releasing electrons when struck by photons from sunlight. The lower layer acts as a collector and is electron-deficient. When joined by a wire, the displaced electrons flow from emitter to collector creating a small potential difference, which is increased first by connecting multiple cells in series and then by connecting additional panels.

To provide a residential solar solution, the DC current generated must be converted to AC by an inverter and its output directed via a control panel to storage batteries or merged with the mains supply as required. In some regions, surplus power can be channelled to service providers by a process called net metering in exchange for discounted tariffs.

Utilising the sun’s energy is not merely an economical option; commercial, industrial, and residential solar solutions are our best hope for a sustainable future.