What is Solar Energy?

Solar refers to energy that is collected from the sun. The sun and wind are renewable energy sources that do not produce green house gases that contribute to global warming. Once the components needed to collect the sun's energy are assembled, solar energy is a free and non-polluting source of power. Currently, there are both State and Federal rebate programs that can lower the total installation cost by more than 1/2. For a typical home there are basically three types of solar energy systems commonly used. Passive solar energy, photovoltaic (PV) solar energy, and solar domestic hot water systems. Wind turbines or generators are also becoming very common for suitable sites. To find out what is currently available through Sun Power RV, please visit our Solar Products pages.

Passive solar energy utilizes the sun's energy to heat, cool, and light a building without any moving parts. There are not any mechanical or electrical components of a passive solar system. Basically all houses are solar. The question is how does your house utilize the available energy from the sun? All home designs and types of construction can benefit from basic passive solar energy principles. Site orientation, properly sized roof overhangs, and window size and location are simple design factors that can greatly affect a homes heating and cooling bill. A home situated with its long axis running east and west can benefit the most from passive solar.                             

The ideal orientation for a solar house is with its long axis perpendicular to true south. Within 20 degrees of true south, the cost in solar gain is minimal, but as the orientation shifts more drastically, the house will significantly lose solar benefits.

Roof overhangs on the south of a building can keep the summer sun out and allow the winter sun in. Too many windows on the west side are hard to shade from the intense western sun without providing large covered porches or some other means to block the hot afternoon sun. A balance must be struck between the amounts of window glazing, your views, and the additional heating or cooling windows can provide. Properly designed roof overhangs help with cooling in the summer and heating in the winter.                                  

Photovoltaic (PV) solar systems utilize the sun's energy to produce electricity for your home or recreational vehicle (RV). The photovoltaic process is a direct conversion of sunlight into DC electricity. That DC electricity can be used directly to power appliances and can be stored in batteries for later use. By installing an inverter on a PV system the DC electricity can be converted into AC electricity that can be utilized in the home and sent back to the utility company to lower your electric bill. Optimum efficiency from a home's photovoltaic solar system requires that the PV panels be oriented true south and be set at an angle equal to the latitude for the site (for a stationary system). Increased efficiency can be obtained by mounting the panels on a tracking system that follows the sun. This type of system requires motors and moving parts and could require a technician to lower the tilt angle of the panels in the summer and raise the tilt angle of the panels in the winter.

Optimum orientation (azimuth and tilt angle) for stationary (fixed) PV panels in Steamboat Springs, Colorado would face true south (0 degrees azimuth angle) and 40 degrees tilt up from the ground plane. This example shows the PV panels incorporated into the roof. The south facing roof has a 10:12 pitch (great for shedding snow yet very steep for roofers). Mounting brackets can be used to raise PV panels off the roof and set the proper tilt angle.

A home photovoltaic solar system can consist of PV modules, a charge controller, storage batteries, a synchronous inverter, the existing AC load center (panel box), and the main service panel containing the utilities disconnect and meter. Storage batteries are only required if the home is not connected to the grid or if the homeowner desires an additional source of power if the utility grid shuts down.

The best advantage to solar and wind power is that they are renewable energy sources that do not contribute to global warming.                 

Solar domestic hot water systems are active systems in which water or antifreeze is circulated from a solar collector through a storage reservoir. The water in the reservoir or storage tank is heated by the circulated fluid and reduces the homes gas or electric consumption for water or space heating. Water that is heated by the sun is especially cost effective for spas and swimming pools. Proper care and maintenance of these systems must be utilized in order to prevent leaks and bursting pipes.  Have a question?  Ask Us!

Solar Glossary

Alternating current (AC):  Electric current in which the direction of flow is reversed at frequent intervals.  A typical home is supplied with 110 and 220 volt AC current at 60 cycles per second or 60Hz.

 

Altitude:  The angle between the horizon (a horizontal plane) and the sun's position in the sky, measured in degress.  At solar noon the altitude of the sun varies greatly from summer to winter.

 

Ampere (A) or amp:  The unit for electric current or the flow of electrons.  A typical home will have circuits rated at 15 and 20 amps.

 

Angle of incidence: Angle, which references the sun's radiation striking a surface.  Solar panels that are mounted at a 90-degree angle to the sun have the best performance.

 

Array:  Any number of photovoltaic modules connected together to provide a single electrical output at a specified voltage.  Voltage supplied by an array is typically 12, 24, or 48 volts.

 

Azimuth:  Angle between true south and the location of the sun.  Measured in degrees east or west of true south.

 

Battery:  Two or more cells electrically connected for storing energy.  Automobile and RV batteries typically are 12 volt comprised of six cells of 2 volts each.

 

Battery cycle life:  The number of cycles, to a specified depth of discharge, that a battery can undergo before failing to meet its specified capacity.

 

Blocking diode: A semi-conductor device connected in series with a PV module and a storage battery to prevent a reverse current discharge of the battery.

 

Boon docking: Staying in your recreational vehicle away from an electrical power source.  Solar panels on your RV will increase the number of days you can stay in the boondocks.

 

Cell:  The basic unit of a photovoltaic module.  Also commonly used to describe the basic unit of batteries.

 

Charge controller:  A device that controls the charging rate and/or state of charge for batteries.

 

Compact fluorescent lights: Lights that use a lot less energy than regular (incandescent) light bulbs.  A fluorescent light bulb rated at 60 watts produces the same amount of light as a 60 watt incandescent light bulb yet use only 14 watts of power versus 60 watts.  Fluorescent light bulbs typically last many times longer than incandescent light bulbs.

 

Current:  The flow of electricity, measured in amps, in a conductor (copper wiring) between two points.

 

Days of autonomy: The number of consecutive days a stand-alone system battery bank will meet a defined load without solar energy input.  A cloudy, stormy day would result in one day of autonomy.

 

Deep cycle battery:  Type of battery that can be discharged to a large fraction of capacity many times without damaging the battery.  Automobile, RV, and marine batteries are not deep cycle batteries.  Deep cycle batteries are heavy (approximately 75 lbs.) and are commonly used on electric forklifts and home solar systems where batteries are used.

 

Direct current (DC): Electric current in which electrons flow in one direction only.  Solar modules produce DC current.  Batteries receive and provide DC current.

 

Disconnect: Switchgear used to connect or disconnect components of a PV system for safety or service.

 

Electric circuit:  Path followed by electrons (electricity) through a conductor (wiring), including the appliances or devices using the electricity, and returning to the source.  Household electric circuits are typically 15 and 20 amps.

 

Electric grid:  An integrated system of electricity distribution.  Power plants produce the electricity that is distributed to your home on the electric grid.  In Steamboat Springs, Colorado, Yampa Valley Electric Association (YVEA) purchases electricity form the power plants in Hayden and Craig (Xcel Energy) and distributed it to their customers on their electric grid.

 

Energy:  The ability to do work.  Stored energy becomes working energy when we use it.  Energy uasage is expressed as kilowatt-hours (kWh) for electricity.

 

Fossil fuels: Fuels formed in the ground from the remains of dead plants and animals.  It takes millions of years to form fossil fuels.  Oil, natural gas, and coal are fossil fuels.

 

Global warming:  A build up of green house gases, like carbon dioxide, in the earth's atmosphere that traps the ultraviolet rays of the sun causing a net increase in the earth's temperature.  Burning of fossil fuels like gasoline and diesel in automobiles and coal in electric power plants contribute to global warming.  Burning of forests also contribute to global warming by producing carbon dioxide while being burned and eliminating the photosynthesis that would have reduced carbon monoxide if the forests were not removed.

 

Grid:  See "electric grid."

 

Grid-connected:  A PV system in which the PV array supplies power to the grid.  The electric grid acts as the battery source for a PV system.  When a home needs more power it can get it from the grid.  When a PV system on a home produces excess power it can send it back to the grid.  Typically excess energy produced from a home PV system will be credited dollar-for-dollar back to the consumer.

 

Hybrid system: A PV system that includes other sources of electricity generation, such as wind or fossil fuel generators.

 

Insolation:  Sunlight, direct or diffuse, from solar radiation.  Usually expressed in watts per square meter.

 

Insulation:  Materials that reduce the rate or slow down the movement of heat.  Insulating materials include fiberglass, foam-board, and cellulose.

 

Inverters:  Devices that convert DC electricity into AC electricity.  Your utility company must approve the inverter from your PV system to insure that the power being produced meets their specifications.

 

Load:  Anything in an electrical circuit that, when the circuit is turned on, draws power from that circuit.

 

Module: See "photovoltaic module."

 

NEC: An abbreviation for the National Electrical Code, which contains safety guidelines and required practices for all types of electrical installations.  Article 690 pertains to solar photovoltaic systems.

 

Nonrenewable fuels:  Fuels that cannot be easily made or renewed.  We can use up nonrenewable fuels.  Oil, natural gas, and coal are nonrenewable fuels.

 

Orientation:  Placement according to the compass directions, north, south, east, west.  Proper orientation of photovoltaic panels is critical for maximum power production.

 

Panel:  See "photovoltaic panel."

 

Parallel connection:  A way of joining two or more electricity-producing devices such as PV cells or modules, or batteries by connecting positive leads together and negative leads together; such a configuration increase the current but the voltage is constant.  Connecting two RV batteries in parallel will double the current and keep the voltage the same.

 

Passive solar building:  A building that utilizes non-mechanical, non-electrical methods for heating, cooling and/or lighting.  Orienting the long axis of the building east and west will maximize the southern exposure of the building.  Utilizing properly sized overhangs on the south side of the building will maximize solar heat gain in the winter and minimize solar heat gain in the summer.

 

Peak sun hours: The equialent number of hours per day when solar irradiance averages 1000 w/m² (full sun).  For Steamboat Springs, Colorado (north latitude 40°30') the average peak sun hours per day is 5.4.  There is an average of 5.7  peak sun hours for San Diego, California (north latitude 32°44').

 

Photovoltaic (PV): Pertaining to the direct conversion of photons of sunlight into electricity.

 

Photovoltaic array: An interconnected system of PV modules that function as a single electricity-producing unit.  The modules are assembled as a discrete structure, with common support or mouting.  In smaller systems, as array can consist of a single module.

 

Photovoltaic panel:  Often used interchangeably with PV module, but more accurately used to refer to a physically connected collection of modules.

 

Photovoltaic system:   A complete set of components for converting sunlight into electricity by the photovoltaic process, Including the array and balance of system components.

 

Rectifier:  A device that converts AC to DC.  See "inverter."

 

Remote site:  Site, which in not located near the utility grid (off-grid).

 

Renewable energy:  Renewable energy is a source of energy that cannot be depleted or used up.  Fossil fuels like coal, natural gas, and oil are finite sources of energy and are not renewable.  Solar, wind, and hydroelectric power are infinite in supply and are renewable energy sources.  Wood, bio-diesel derived from soybeans or other plants, and alcohol derived from corn are all renewable energy sources because they can be grown again.  These sources of fuel do contribute to global warming, however, there impact isn't as large if new plants are cultivated because their growth consumes carbon dioxide.

 

Series connection:  A way of joining electrical equipment by configuring positive leads to negative leads; such a configuration increase the voltage while current remains the same.

 

Short circuit current (Isc):  The current flowing freely from a photovoltaic cell through an external circuit that has no load or resistance; the maximum current possible.

 

Sine wave inverter:  An inverter that produces utility-quality, sine wave power forms.

 

Solar energy:  The energy from the sun.  For example, the heat builds up in your car when the windows are closed is solar energy.

 

Solar noon:  That moment of the day that divides the daylight hours for that day exactly in half.  To determine solar noon, calculate the length of the day from the time of sunset and sunrise and divide by two.  The moment the sun is the highest in the sky.  If the sunset is 6:00pm and the sunrise is 7:00am, solar noon would be at 12:30pm.

 

Stand-alone PV system:  An autonomous or hybrid photovoltaic system not connected to a grid.  Most stand-alone systems require batteries for storage.

Sun Power RV:  The new name for Solar Home and RV.

Surge capacity:  The ability of an inverter or generator to deliver high currents momentarily required when starting a motor.

 

Thermal mass:  Materials, typically masonry, that store heat in a passive solar home.

 

Tilt angle:  Angle of inclination of a collector as measured in degrees from the horizontal.  For maximum performance solar collectors/modules should be set at a perpendicular to the sun.

 

Transformers:  An electromagnetic device used to convert AC electricity from the transformer to the electric distribution system.

 

Utility-interactive inverter:  An inverter that can function only when tied to the utility grid, and uses the prevailing line-voltage frequency on the utility line as a control parameter to ensure that the PV system's output is fully synchronized with the utility power.

 

Volt (V):  A unit of measure of the force given the electrons in an electric circuit.  One volt produces one ampere of current when acting against a resistance of one ohm.

 

Watt (W):  The unit of electric power, or amount of work.  W = V X A

 

Watt-hour (Wh):  A quantity of electrical energy when one watt is used for one hour.