| According to many renewable energy experts, a | | | | PV, or microhydropower) is not creating enough |
| stand-alone hybrid system that combines | | | | electricity to endure load supplies. To provide |
| generation sources, such as wind and PV, offers | | | | electricity over lengthy periods, renewable |
| several advantages over a single generation | | | | systems require deep-cycle batteries. These |
| system. | | | | batteries, commonly lead-acid, are designed to |
| In much of the United States, wind speeds are | | | | regularly discharge and recharge 80% of their |
| low in the summer when the sun shines brightest | | | | capacity hundreds of times. Automotive batteries |
| and longest. The wind is great in the winter when | | | | are shallow-cycle batteries and must not be used |
| there is less sunlight. Since the greatest operating | | | | in renewable systems since they are planned to |
| times for wind and PV occur at diverse times of | | | | discharge just about 20% of their capacity. If |
| the day and year, hybrid systems are more likely | | | | drawn much under 20% capacity more than a |
| to yield energy once you need it. For the times | | | | few dozen times, the battery will be damaged |
| when neither the wind generator nor the PV | | | | and will no longer be able to take a charge. |
| modules are producing electricity (for example, by | | | | The cost of deep-cycle batteries depends on the |
| night whilst the wind is not blowing), most | | | | type, capacity (amperehours), the climatic |
| stand-alone systems provide energy through | | | | conditions in which it will run, how frequently it will |
| batteries and/or an engine-generator powered by | | | | receive maintenance, and the types of chemicals |
| fossil fuels. | | | | it uses to store and make available electricity. An |
| If the batteries run low, the engine-generator can | | | | off-grid PV or wind system could have to be |
| be run by full power until the batteries are | | | | sized to save a sufficient amount of energy in the |
| charged. Adding a fossil-fuel powered generator | | | | batteries to endure power demand during few |
| makes the system more complicated, but new | | | | days of gray weather or low winds. This is |
| electronic controllers can run these complicated | | | | recognized as days of autonomy. Consult your |
| systems without doubt. Adding an | | | | dealer previous to selecting batteries for your |
| engine-generator can furthermore reduce the | | | | system. |
| quantity of PV modules and batteries in the | | | | Charge Controller. |
| system. Keep in mind that the storage capability | | | | The charge controller regulates the flow of |
| should be generous enough to supply electrical | | | | electricity from the generation source to the |
| needs for the period of non-charging periods. | | | | battery and the load. The controller keeps the |
| Battery banks are typically sized for one to three | | | | battery fully charged with no overcharging it. |
| days of function. An all-purpose rule is to design | | | | When the load is drawing energy, the controller |
| the renewable energy system to provide 80% of | | | | allows the charge to flow from the generation |
| the energy and use fossil fuels for the residual | | | | source into the battery, the load, or both. When |
| 20%. | | | | the controller senses that the battery is full, it |
| Balance-of-System (BOS) Equipment | | | | stops the flow of the charge from the generation |
| In addition to wind turbines, PV modules, or a | | | | source. Many controllers will also feel when loads |
| microhydropower generator, you should pay for | | | | have taken too much electricity from batteries |
| BOS equipment. This could include battery charge | | | | and will bar the flow until enough charge is |
| controllers, batteries, inverters, wires, conduit, a | | | | restored to the batteries. This last attribute can |
| grounding circuit, fuses, safety disconnects, | | | | greatly enlarge the battery's life span. The cost of |
| outlets, metal structures for supporting the PV | | | | controllers commonly depends on the ampere |
| modules, and any other components that are part | | | | capacity at which your renewable system will run |
| of the system. | | | | and the monitoring features you would like. |
| In very little systems, DC appliances run directly | | | | Alternating-Current System Equipment Inverter. |
| off the batteries. If you like to use standard | | | | Alternating-current (AC) systems too require an |
| appliances that require normal household | | | | inverter, which changes the DC electricity created |
| alternating current (AC), however, you should | | | | by renewable systems and stored in batteries |
| install an inverter to convert DC electricity to AC. | | | | into AC electricity. Various types of inverters yield |
| Although the inverter to some extent lowers the | | | | a diverse quality of electricity. For example, |
| overall efficiency of the system, it allows the | | | | illumination, televisions, and power tools can run on |
| home to be wired for AC, a definite plus with | | | | lower-quality electricity, but computers and other |
| lenders, electrical code officials, and prospect | | | | sophisticated electronic equipment require the |
| home buyers. We'll discuss BOS configurations | | | | highest-quality electricity. So, you must match the |
| initially for loads requiring direct current, then for | | | | electricity quality required by your loads with the |
| loads needing alternating current. In grid-connected | | | | power quality created by the inverter. |
| systems, the single extra equipment required is an | | | | Inverters for most stand-alone applications (i.e., |
| inverter that makes the turbine output electrically | | | | those systems not connected to the electricity |
| compatible with the utility grid. No batteries are | | | | grid) cost less than $1 per rated output watt. The |
| required. Work with the manufacturer and your | | | | cost is affected by few factors, including the |
| regional utility on this process. When examining the | | | | quality of the electricity it needs to yield; whether |
| expenses of wind turbines, PV modules, or | | | | the incoming DC voltage is 12, 24, 36, or 48 volts; |
| microhydropower generators, remember that | | | | the amount of AC watts your loads require when |
| these expenses do not include the cost of BOS | | | | they are operating normally; the amount of |
| equipment. | | | | additional surge energy your AC loads need for |
| Direct-Current System Equipment Battery. | | | | short periods; and whether the inverter has any |
| In off-grid systems, the battery stores electricity | | | | additional features such as meters and indicator |
| for work at night or for meeting loads throughout | | | | lights. |
| the day as the generation source (wind turbines, | | | | |