KOHILO University

Glossary of Terms

Aggregation Bundling several wind energy projects together so that they are treated as one larger project (when purchasing turbines, interconnecting, or maintaining a project, for example,) in order to spread out costs over more turbines or projects. This can have the effect of improving project economics and also provides the basis for KOHILO’s finance model and its use of Wind Energy Investment Funds (WEIFs).
Aggregate Net Meter (ANM) Allows a single customer with multiple meters, and therefore multiple utility accounts, to offset his aggregate load with a single renewable energy system. In some cases, a customer physically connects his or her meters together in order to distribute the energy from a single system to multiple accounts, e.g. connecting 5 meters on one farm. More typically, a customer accomplishes this distribution virtually, by allocating net metering credits from a single renewable energy system to that customer’s multiple utility bills, through Virtual Net Metering (see definition below).
Airfoil The cross section profile of the leeward side of a wind generator blade. Designed to give low drag and good lift. Also found on an airplane wing.
Anemometer An instrument used to measure the velocity, or speed, of the wind.
Angle of Attack The angle of relative air flow to the blade in a wind turbine.
Armature The moving part of an alternator, generator or motor. In many alternator designs, it carries the magnets and is attached to the blades and hub. Also called a Rotor.
Availability Factor The percentage of time that a wind turbine is able to operate and is not out commission due to maintenance or repairs.
Balancing With wind turbine blades, adjusting their weight and weight distribution through 2 axes so that all blades are the same. Unbalanced blades create damaging vibration.
Betz Coefficient 59.3 percent. This is the theoretical maximum efficiency at which a wind generator can operate, by slowing the wind down. If the wind generator slows the wind down too much, air piles up in front of the blades and is not used for extracting energy.
Blade The flat panels on a wind turbine that are connected to a center shaft that converts the push of the wind into a circular motion in a wind turbine.
Braking Syste A device to slow a wind turbine’s shaft speed down to safe levels electrically or mechanically.
Capacity Factor A measure of the productivity of a wind turbine, calculated by the amount of power that a wind turbine produces over a set period of time, divided by the amount of power that would have been produced if the turbine had been running at full capacity during that same time interval.
Chord The width of a wind turbine blade at a given location along the length.
Commercial Scale Wind Wind energy projects greater than 100 kW where the electricity is sold rather than used on-site. This category can include large arrays of 100 or more turbines owned by large corporations, a single locally-owned wind turbine greater than 100 kW in size, or anything in between.
Community Wind ocally-owned, commercial-scale wind projects that optimize local benefits. Locally-owned means that one or more members of the local community has a significant direct financial stake in the project other than through land lease payments, tax revenue, or other payments in lieu of taxes.
Cut-In Speed The wind speed at which the turbine blades begin to rotate and produce electricity, typically around 10 miles per hour.
Cut-Out Speed The wind speed at which the turbine automatically stops the blades from turning and rotates out of the wind to avoid damage to the turbine, usually around 55 to 65 miles per hour.
Distributed Generation small-scale power generation technology that provides electric power at a site closer to customers than the central station generation. The term is commonly used to indicate non-utility sources of electricity, including facilities for self-generation.
Downwind Turbine efers to a Horizontal Axis Wind Turbine in which the hub and blades point away from the wind direction, the opposite of an Upwind turbine.
Furling he act of a wind generator yawing out of the wind either horizontally or vertically to protect itself from high wind speeds.
Grid-Connected System A residential electrical system such as solar panels or wind turbines which are connected to the electrical grid. In such systems the grid serves as a battery backup for the residential system for those times when there is no sun or wind.
Guy Anchor A concrete or metal base which attaches windtower guy wires securely to the earth.
Guy Wire A strong metal cable or wire which attaches a tower to the ground.
Horizontal Axis Wind Turbine “normal” wind turbine design, in which the shaft is parallel to the ground, and the blades are perpendicular to the ground.
Hub The central part of the wind turbine, which supports the turbine blades on the outside and connects to the low-speed rotor shaft inside the nacelle.
Hybrid system The combination of multiple energy producing technologies such as photovoltaic systems combined with small wind turbine systems.
Hybrid system The combination of multiple energy producing technologies such as photovoltaic systems combined with small wind turbine systems.
Inverter A device that converts direct current electricity to alternating current either for stand-alone systems or to supply power to an electricity grid
Interconnection Agreemen An agreement between an electrical company and the interconnection customer which outlines the interconnection requirements, costs and billing agreements, insurance requirements, and ongoing inspection, maintenance, and operational requirements.
Kilowatt A measure of 1,000 watts of electrical power.
Kilowatt-Hour (kwh) A measure of electrical energy equivalent to a power consumption of 1,000 watts for 1 hour.
Letter of Intent (LOI) A document outlining an agreement between two or more parties before the agreement is finalized. LOIs resemble written contracts, but are usually not binding on the parties in their entirety. Many LOIs, however, contain provisions that are binding, such as non-disclosure agreements or a covenant to negotiate in good faith.
Megawatt A unit of power equal to one million watts, especially as a measure of the output of a power station.
Met Tower A group of instruments (including anemometers and wind vanes) that collectively measure various meteorological parameters such as wind speed, wind direction, and temperature at various heights above the ground. met is short for meteorological.
Nacelle The structure at the top of the wind turbine tower just behind (or in some cases, in front of) the wind turbine blades that houses the key components of the wind turbine, including the rotor shaft, gearbox, and generator.
Net Meter Allows residential and commercial customers who generate their own electricity from solar power to feed electricity they do not use back into the grid. Many states have passed net metering laws. In other states, utilities may offer net metering programs voluntarily or as a result of regulatory decisions. Differences between states’ legislation and implementation mean that the benefits of net metering can vary widely for customers in different areas of the country.
Power Curve The instantaneous power output of a specific turbine design at various wind speeds. Used with wind resource data to determine the potential for electricity generation at a project site.
Power Purchase Agreement (PPA) A contract between two parties, one who generates electricity for the purpose of selling (the seller) and one who is looking to purchase electricity (the buyer). The PPA defines all of the commercial terms for the sale of electricity between the two parties, including when the project will begin commercial operation, schedule for delivery of electricity, penalties for under delivery, payment terms, and termination. A PPA is the principal agreement that defines the revenue and credit quality of a generating project and is thus a key instrument of project finance. There are many forms of PPA in use today and they vary according to the needs of buyer, seller, and financing counterparties.
Rated Wind Speed The wind speed at which the turbine is producing its nameplate-rated power production. For most small wind turbines this is around 30 to 35 miles per hour; KOHILO’s turbines begin to generate power at 3 MPH.
Remote Net Meter (RNM Allows eligible customer-generators to designate net metering credits from equipment located on property which they own or lease to any other meter that is located on property owned or leased by the customer, and is within the same utility territory and load zone as the net metered facility. Credits will accrue to the highest use meter first, and as with standard net metering, excess credits may be carried forward from month to month.
Rotor Comprises the spinning parts of a wind turbine, including the turbine blades and the hub.
Site Lease Agreement A contract between a lessor and a lessee that allows the lessee rights to the use of a property owned or managed by the lessor for a period of time. The agreement does not provide ownership rights to the lessor; however, the lessor may grant certain allowances to modify, change or otherwise adapt the property to suit the needs of the lessee. During the lease period, the lessee is responsible for the condition of the property.
Start-Up Speed The windspeed at which a wind turbine rotor starts to rotate. It does not necessarily produce any power until it reaches cut-in speed.
Tail Boom A strut that holds the tail (Vane) to the wind generator frame.
Thrust Bearing A bearing that is designed to handle axial forces along the centerline of the shaft–in a wind generator, this is the force of the wind pushing back against the blades.
Tower The base structure that supports and elevates a wind turbine rotor and nacelle.
Turbine A device for converting the flow of a fluid (air, steam, water, or hot gases) into mechanical motion that can be utilized to produce electricity.
Twist In a wind generator blade, the difference in pitch between the blade root and the blade tip. Generally, the twist allows more pitch at the blade root for easier startup, and less pitch at the tip for better high-speed performance.
Vane A large, flat piece of material used to align a wind turbine rotor correctly into the wind. Usually mounted vertically on the tail boom. Sometimes called a Tail.
Variable Pitch Turbine A type of wind turbine rotor where the attack angle of the blades can be adjusted either automatically or manually.
Vertical Axis Wind Turbine A wind generator design where the rotating shaft is perpendicular to the ground, and the cups or blades rotate parallel to the ground.
Virtual Net Meter (VNM) Allows multiple customers, with multiple meters and associated utility accounts, to receive the benefits of a single renewable energy system. VNM (multiple customers, multiple meters) is increasingly distinguished from meter aggregation (single customer, multiple meters). With VNM, the net-metered generation facility is behind one of the customer’s meters and the customers’ utility distributes the resulting net metering credits on the participating customers’ bills. In this way, VNM can facilitate shared renewable energy, where multiple customers have “shares” or interests in a single renewable energy system and receive bill credits based on that share.
Watt The rate of energy transfer equivalent to one ampere under an electrical pressure of one volt. One watt equals 1/746 horsepower, or one joule per second. It is the product of voltage and current (amperage).
Waveform The shape of the phase power at a certain frequency and amplitude.
Wind Monitoring System Also termed met tower, a group of instruments (including anemometers and wind vanes) that collectively measure various meteorological parameters such as wind speed, wind direction, and temperature at various heights above the ground.
Wind Power Class A system designed to rate the quality of the wind resource in an area, based on the average annual wind speed. The scale ranges from 1 to 7 with 1 being the poorest wind energy resources and 7 representing exceptional wind energy resources.
Wind Resource The wind energy available for use based on historical wind data, topographic features, and other parameters.
Wind Rose A circular plot used to define certain characteristics about wind speed and direction observed at a monitoring location.
Wind Shear A term and calculation used to describe how wind speed increases with height above the surface of the earth. The degree of wind shear is a factor of the complexity of the terrain as well as the actual heights measured. Wind shear increases as friction between the wind and the ground becomes greater. Wind shear is not a measure of the wind speed at a site.
Wind Speed The rate at which air particles move through the atmosphere, commonly measured with an anemometer.
Wind Vane A device used to measure wind direction.
Windmill A device that uses wind power to mill grain into flour. Informally used as a synonym for wind generator or wind turbine, and to describe machines that pump water with wind power.

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