Paris Pv Presentation Part1

Fred Paris [email protected] Co-op Power Sustainable Energy Summit 2009 Page 1 of 9

Solar Power – Part of the Green Energy Solution in Massachusetts

Fred Paris for: Co-op PowerSustainable Energy SummitUMass AmherstMay 1,2009

Interactive (Grid-Tied) Solar

Overview An interactive, or what is sometimes called grid-tied, photovoltaic solar system canbe designed to provide as little or as much of the electricity a home requires.

System sizes can range from small starter systems to larger arrays sized to eliminatea home’s electric bill. Once the system is installed a homeowner could expect to gainsolar energy for 20 years or more. There are many examples of systems 25 years oldor more still performing at more than 80% of their original energy output.

Interactive systems are for homes that are connected to a public utility. There are twosignificant advantages to interactive systems; first, the occupants of the home neednever worry about where their electricity is coming from. If the solar resource is notavailable or if the electrical load is higher than the array can support, the utility willsupply up to 100% of their energy load. Second, interactive systems do not requirebatteries. Batteries typically add thousands of dollars in costs and requireknowledgeable and frequent maintenance.

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How Solar Works

How SolarWorks

When a home has an interactive solar PV system, the electrical devices in a homewill use the owner’s solar power first and then look to the utility to cover theadditional power required. That makes it easy to understand that the larger the PVsystem the less energy a homeowner will buy from the utility, and the lower theirmonthly bill will be. It also explains how a homeowner can start with a small systemand incrementally add capacity as they watch their energy bill decline.

The other significant benefit of an interactive PV system is net-metering. Under net-metering arrangements - available anywhere in Massachusetts – if a home’s PVsystem is generating more energy that is being used, the energy goes back to theutility for full retail credit. So, if you are paying 18¢ a kilowatt-hour (kWh) theutility will pay you the full 18¢ for every kWh you send back. Think about thoselong hot summer days when the house is empty – it may all go back to the utility.

There are four key elements to a solar photovoltaic system: the solar modules, theinverters, the production meter, and the typical electrical switches and wiringassociated with any electrical system.

The SolarModules

When sunlight strikes a solar module, the characteristics of silicone layered withother materials causes electrons to start flowing. Get enough electrons moving andyou create electrical current. Give that current a pathway to follow, and then joinmultiple modules and pathways together, and you can design and create systems ofany size. A small starter system may only have a few solar modules while some ofthe largest commercial systems cover acres of land.

Multiple solar modules wired together form a solar array. An advantage ofresidential and commercial arrays is that they can be added to incrementally withoutdiscarding the components installed earlier. So a homeowner might install a smallsystem and later add more modules and another inverter to build any size they want.

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Fred Paris [email protected] Co-op Power Sustainable Energy Summit 2009 Page 3 of 9

How Solar Works, Continued

The Inverter(s) The inverter is the device that changes Direct Current (DC) to Alternating Current(AC). Solar modules produce DC but our homes require AC. AC is also what theutility delivers to the home. For most homes the inverter will be a breadbox-sizeelectrical component installed by an electrician near the circuit breaker panel.Inverters monitor and run on power from the utility. This serves a couple ofpurposes; first, if the utility goes down, the inverter shuts down. We do not wantsolar systems feeding the grid with utility linemen at work. The invertersynchronizes the AC sine wave to the utility’s sine wave, allowing for net metering.

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Fred Paris [email protected] Co-op Power Sustainable Energy Summit 2009 Page 4 of 9

How Solar Works, Continued

The ProductionMeter

Unlike the utility meter, the homeowner owns the production meter. Thehomeowner’s meter only measures the energy produced by their solar system. Thisallows the homeowner to see exactly how much power their system is producing. Inmost cases, a production meter is a required part of a residential solar system.

One of the additional benefits of a residential solar system is the production andaccounting for virtual Renewable Energy Credits (RECs). A discussion of RECs isbeyond the scope of this paper, but for every kilowatt of energy a solar systemproduces, RECs are generated in the owner’s name. RECs are then sold as acommodity. The production meter helps the homeowner validate RECs.

Switches andWiring

Everything gets connected together. The modules are wired together, then to theinverter and the production meter. AC and DC switches are installed enabling theowner or the utility to shut down the entire system as required by the NationalElectric Code (NEC).