SOLOSOL - Glossary of Solar Terms
| Absorption Charge | The second stage of three-stage battery charging. Voltage remains constant and current tapers as internal battery resistance increases during charging. (Ensures complete charging.) |
| Alternating Current (AC) | The type of electrical power supplied by utilities or made when a generator is run. The unique characteristic of this form of electricity is that it reverses direction at regular intervals. For example, 220 Vac 50 Hz. power reverses flow 50 times a second, hence the rating 50 Hz. (cycles). |
| Amp | A measurement of the flow of electrical current. One amp is equal to the electric force of one volt acting across the resistance of one ohm. |
| Amp Hour | One amp of electrical current flowing for one hour. Expresses the relationship between current (amps) and time. (OHMS law I =V/R) |
| Array | A group of solar electric modules wired together. |
| Bulk Charge | The first stage of three-stage battery charging. Current is sent to batteries at the maximum rate they will accept while voltage rises to full charge level. |
| Charge Controller | Photovoltaic charge controllers or voltage regulators control the amount of energy from the PV panels going into the batteries. In particular they protect the batteries from overcharging, subsequent gassing, loss of electrolyte and possible plate damage. |
| Current | Current is the rate of flow of electricity along a wire and is measured in amps (A). Current that flows in a single direction is known as direct current DC. A current that changes direction is called alternating current or AC. Batteries store and transfer on direct current. |
| Direct Current (DC) | The type of electricity stored in batteries and generated by solar electric devices. Current flows in a single direction. |
| Efficiency | Efficiency is the ratio of output energy to input energy expressed as a percentage. Energy efficient devices use less energy to perform their task. |
| Electrolyte | A conductive medium in which the flow of electricity takes place; this is the liquid found inside storage batteries. |
| Energy | Energy is a measure of how much electricity is supplied and is the product of wattage and time. The amount of electricity is either produced by a generator or consumed by an appliance. The unit of energy is the watthour (Wh), which is watts multiplied by time (hours). The watthour (Wh) is the unit of energy commonly used in small renewable energy systems. |
| Float Charge | The third stage of three-stage battery charging. After batteries reach full charge, charging voltage is reduced to a lower level to reduce gassing (boiling of electrolyte) and prolong battery life. This is often referred to as a maintenance charge, since rather than charging a battery, it keeps an already-charged battery from self-discharging. |
| Grid | When used in reference to utility power, it refers to a system of electrical transmission and distribution lines. |
| Grid-connect | Also known as Line-tie, an electrical system that is connected to a utility distribution grid. For example, Trace SW line-tie inverters are designed to connect to and interact with utility power. |
| Grid Open | The inverter (Trace SW) can tell when there is no current being delivered to the grid and it will disconnect. This is used when a disconnected switch is opened or the power line which feeds the installation is cut. This protective system may require up to one second to respond. |
| Grid Shorted | Normally, when the utility power fails, the Trace SW inverter momentarily tries to power the entire neighborhood. This condition looks like a short circuit to the inverter and causes it to reach the over-current protection setting and shuts off. It then opens it internal relay and disconnects from the utility grid. This protective system operates instantly (under four milliseconds). |
| Ground Fault Protection (GFP) | A circuit protection device that prevents the flow of electrical current to earth if a short circuit is present. Usually required in wet locations-e.g. for outdoor, kitchen and bathroom circuits. |
| Hertz (Hz.) | The frequency, or number of times per second, that the flow of AC electricity reverses itself. Also referred to as cycles (see alternating current). |
| High Battery Protection | A control circuit that disconnects charge current flowing to a battery when voltage reaches a dangerously high threshold. Prevents damage created by excess gassing (or boiling) of electrolyte. |
| Hydrometer | A simple device that measures the specific gravity of battery electrolyte. Specific gravity readings express state of charge/discharge of battery. |
| Idle Current | The amount of electrical power required to keep an inverter ready to produce electricity on demand. |
| Inverter | Inverters convert DC electricity stored in batteries into 220V AC power required to run conventional appliances. These are known as stand alone inverters. Some inverters can also feed power back into the grid and are known as ‘Grid Connect’ or synchronous inverters. More information on inverters can be found on our ‘Choosing an Inverter’ page. |
| Islanding | This occurs when the grid has failed and the "neighborhood" that the inverter is powering requires the same amount of power that the inverter can supply. This balanced condition is often called "islanding". The islanding detection circuit checks the grid condition on each cycle. The inverter watches the utility grid and waits for it to rise a couple of volts before it begins to invert again. This is done on each cycle when SELL mode is activated. Typically, disconnection is achieved in a few cycles after the utility has failed. If a large electric motor is connected, it may provide enough generator capacity that the inverter thinks the grid is still connected. This can fool this protective system. Two additional protective systems are provided to then handle this condition over/under frequency and over/under voltage detection. |
| Kilowatt (kW) | One thousand watts of electricity. Ten 100-watt light bulbs use one Kilowatt of electrical power. |
| Kilowatt hour (kWh) | One kW of electrical power used for one hour. The most common measurement of electrical consumption, most grid connected electrical meters measure kWh for billing purposes. |
| LED (Light Emitting Diode) | A device used to display various status functions. |
| Line Loss | A voltage drop caused by resistance in wire during transmission of electrical power over distance. |
| Line-tie | Also known as Grid-connect, an electrical system that is connected to a utility distribution grid. For example, Trace SW line-tie inverters are designed to connect to and interact with utility power. |
| Load | Any device that consumes electricity in order to operate. Appliances, tools, and lights are examples of electrical loads. |
| Low Battery Protection | A control circuit that stops the flow of electricity from batteries to loads when battery voltage drops to dangerously low levels. |
| Maximum Power Point Tracking (MPPT) | - Every PV (solar electric) device has a point where maximum current is delivered. MPPT electronically adjusts the output PV-device output to the maximum power point. |
| Modified Sine Wave | An AC wave form (generated by many inverters) that is a pulse width modified square wave. It consists of a number of very small on/off steps rather than a fully smooth wave. |
| Off Grid | An electrical system that is not connected to a utility distribution grid. |
| Oscilloscope | A device that displays the wave form created by an electrical generating device such as a generator, inverter, or utility. |
| Overload/Over-current Protection | A control circuit designed to protect an inverter or similar device from loads exceeding its output capacity. (A fuse, for example, is an over-current protection device.) All Trace inverters have internal circuitry to protect themselves from overload/over-current conditions. |
| Over/Under Frequency | Since the inverter locked onto the frequency of the utility grid, the frequency of the system will drift out of regulation in a short amount of time during an islanding condition. This protective system may require up to one second to respond. The inverter will shut off and disconnect after the frequency exceeds +/- 1 hertz of the nominal frequency. |
| Over/Under Voltage | - Since the inverter does not regulate the voltage of the utility grid while selling power into it, the AC voltage will drift out of regulation in a short amount of time during an islanding condition. This protective system may require up to one second to respond. The inverter will shut off and disconnect after the voltage exceeds +/- 10% of the nominal AC voltage. |
| Parallel Wiring | A group of electrical devices, such as batteries or PV modules, wired together to increase ampacity, while voltage remains constant. (Two 100 amp hour 12 Vdc batteries wired in parallel will form a 200 amp-hour 12 Vdc battery bank.) |
| Photovoltaic module | Photovoltaic modules (PV) convert sunlight into DC electricity. When connected to a storage battery with a suitable charge controller to prevent overcharging, they will put charge into the battery when exposed to sunlight. Output voltage is fairly constant under all levels of light, but the output power (current measured in Amps) varies with the intensity of light. |
| Photovoltaic System | The components that form a solar electric generating system, usually consisting of PV modules, charge controller, circuit protectors (fuses or breakers) and batteries. |
| Power | The rate at which work is done. The rate at which electricity is either produced by a generator or consumed by an appliance. The unit of power is the watt (W). One watt of power is consumed when one volt causes one amp of current to flow. One thousand watts 1000w is called 1kW. Power = Current x Voltage |
| PV Peak Power | Peak Power (Wp) is the amount of power a PV module can be expected to deliver at noon on a sunny day (standard test conditions) when it facing directly towards the sun. |
| Resistance | The property of a conductor (i.e. connecting cables) which opposes the flow of current through it resulting in the conversion of electrical energy into heat. Resistance has the symbol R, and is measured in Ohms. |
| Series Wiring | A group of electrical devices, such as batteries or PV modules, wired together to increase voltage, while ampacity remains constant. (Two 100 amp hour 12 Vdc batteries wired in series form a 100 amp hour 24 Vdc battery bank.) |
| Sine Wave | The output wave form of an electric generator or utility. A smooth wave going above and below zero is created. This wave form is also produced by sine wave inverters such as the Trace SW and CO-Sine series. |
| Surge Capacity | The amount of current an inverter can deliver for short periods of time. Most electric motors draw up to three times their rated current when starting. An inverter will "surge" to meet these motor-starting requirements. Most Trace inverters have surge capacities at least three times their continuous ratings. |
| Transfer Switch | A switch designed to transfer electricity being supplied to loads (appliances etc.) from one source of power to another. (A transfer switch may be used to designate whether power to a distribution panel will come from a generator or inverter.) |
| Volts | A unit of measure of the pressure in an electrical circuit. Volts are a measure of electric potential. Voltage is often explained using a liquid analogy-comparing water pressure to voltage: a high pressure hose would be considered high voltage, while a slow-moving stream could be compared to low voltage. |
| Watt(s) | A quantitative measurement of electrical power. Watts are calculated by multiplying volts times amps. Using a liquid analogy, watts are similar to liquid flow such as litres or gallons. (watts = volts x amps) |
| Watt Hour (wHr) | Electrical power measured in terms of time. One watt hour of electricity is equal to one watt of power being consumed for one hour. (A one-watt light operated for one hour would consume one watt hour of electricity.) |
Energy that doesn’t cost the Earth...
Solar cells are long lasting sources of energy which can be used almost anywhere. Solar cells provide cost-effective solutions to energy problems in places where there is no mains electricity.
Compared to other renewable sources, they also possess many advantages:
Very reliable: Kyocera modules have a 25 year warranty and a considerably longer life expectancy. The theoretical lifespan of solar modules is 100 to 125 years. The first modules ever manufactured are still producing power after 50 years of service.
Environmentally Friendly: Over its lifetime a single gram of silicon can produce 3,300 kWh of electricity without releasing life threatening toxic and radioactive substances. A single gram of uranium can produce 3,800 kWh of electricity. However, a uranium atom can only be fissioned once, whereas a silicon solar cell can absorb photons repeatedly to generate electricity. Gram for gram, silicon and uranium produce comparable amounts of electricity.
Green Energy: Solar power is an environmentally friendly energy source. By not using fossil fuels to generate electricity, a 1Kw solar power system will prevent about 25 tons of carbon dioxide emissions over its life. That is equivalent to planting about an acre of trees.
Low cost: Calculated over the life expectancy of solar modules, solar power becomes one of the cheapest, hassle-free and pollution-free energy sources available.
Inflation proof: Your investment in solar energy protects you from the spiralling cost of energy. Since January 2004, average (UK) household energy bills have risen by 69% or £407. The average joint bill for gas and electricity now stands at just under £1,000 a year per household. Gas bills alone have risen by 85%. Electricity-only customers have seen 50% rises. In the past year each of the power companies have increased prices twice, with three rises from npower.
