September 03, 2010
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PV Grid Tied Systems

Technology Name:

Solar Electric (Photovoltaic) Grid tied systems

Date Introduced in the market:

1980s

Maturity of the technology:

Mature

Status of development:

Established industry with continuous growth over 5+ years.

Type of energy that can be produced (i.e. thermal, electrical):

Electrical

Typical applications:

To supply solar electricity to the local electrical grid.

Electricity produced is typically either subtracted from total electricity used resulting in a reduced electricity bill (net metering), or sold directly to the grid operator with no direct impact on the residence/facility electricity bill, usually for a price higher than what is paid for delivery of grid electricity (Feed in Tariffs or Standard Offer Contracts).
Batteries or other storage mechanisms can be added to a grid tied system to also provide back up electricity when the grid is not available. Without batteries, electricity is not available from the PV system when there is a power outage from the grid (even if the sun is shinning). Adding batteries increases the cost and reduces the efficiency of the system.

Range of possible dimensions and sizing considerations for the system:

The main components of a grid tied photovoltaic system are the PV modules and the inverter. Additional components include wire, disconnects and electricity meter.

PV panels produce DC electricity and the inverter changes the DC electricity to AC electricity to match the grid. PV panels on the market today come in a variety of sizes and shapes. Mono or poly crystalline panels are typically rigid metal framed panels with glazing and are about 100watts per m2. Amorphous silicone, or thin film, PV panels can be flexible and some products have been designed to replace traditional roofing material. While amorphous panels are more expensive and require more area (approximately 2 xs) to generate the same amount of energy that mono or poly crystalline panels do, they can save money when avoiding costs of additional roofing materials such as asphalt shingles and their flexible characteristics can be an advantage.

PV systems are modular and can be easily added to. Sizing a grid tied PV system is a function of the amount of electricity you want the system to produce, the solar resource and exposure available, space available for the panels and budget. If you plan to add PV panels to your system over time, be sure to size the rest of your system (inverter and wire) to manage the additional panels. Residential grid tied systems can be designed to produce the same amount of electricity consumed by the household over a year, less or more. Energy efficiency and conservation are an important factor in determining the percentage of power consumed by the household the PV system will produce. If the objective is to produce the same amount of electricity as consumed by the household, for every dollar spent on energy efficiency and conservation, 3-5 dollars on PV panels is saved.

RETScreen is free software from NRCan that can assist with sizing a renewable energy system. www.retscreen.net.

Inverters:

Inverters for grid tied residential systems typically range in size from about 1-6 kW and fit neatly on the side of a house. For example, the dimensions of one 5kw grid tied inverter are (755 x 403 x 146 mm) weighs about 26 kilos.

Range of performance of the technology per unit installed:

In Canada, if installed on a fixed mount with a clear southern exposure, expect approx 1-1.3 MWh/KW installed/year. More electricity can be expected if PV panels are mounted on a tracker.

Range of costs per unit of energy and per system (installed, and maintenance costs):

PV systems in Canada cost about $9-12/watt installed.
Enquire about maintenance contracts from your system designer and installer. While maintenance is minimal, expect to pay electrician rates if maintenance is required.

Expected Pay-Back:

The cost to purchase and have installed a PV system is fairly standard however the economics will vary significantly depending on the incentives, programs, rules, and cost of electricity in your jurisdiction. Check with your local utility to see what options are available to you.

Net Metering:

A net metering agreement with your local utility means that your utility credits you the equivalent number of kWhs produced by your system on your bill. In most agreements, your account is cleared regularly (e.g. annually) and any remaining credits are not carried forward, nor are payments made from the utility to the PV producer. Check with your local utility for availability, terms and conditions.

Standard Offer Contract/Feed In Tariff:

So far (2007) Ontario is the only province with a Standard Offer Contract or Feed In Tariff for solar PV. This mechanism is quite popular in Europe and many countries with significant amounts of PV installed use this mechanism. Under a Standard Offer Program/Feed In Tariff, the owner of a grid tied PV system is paid a premium price for the electricity generated by the PV system. The electricity generated by the system does not affect the owner's bill as the PV system's production and the household's consumption are measured with separate meters.

Design, Installation, Maintenance & Operation of Grid tied PV system:
Design of a Grid tied PV system:

Expertise/knowledge required can include: PV system design, electrical, mechanical, general construction, and roofing.

Installation of a Grid tied PV system:

Installation of a grid tied PV system requires a licensed electrician. In addition, expertise/knowledge required can include: PV installation, general construction skills, roofing.

Maintenance of a Grid tied PV system:

Grid tied PV systems are virtually maintenance free.
If batteries are added to the system for additional back up power storage, they must be monitored and maintained regularly. Typical batteries used in solar systems will need to be replaced or refurbished every approx 5-20 years, dependent on battery technology.

Operation of a Grid tied PV system:

Can be monitored and operated by homeowner with instruction from contractor/installer.

Training for designers and installers:

CanSIA is working with colleges to implement training programs for designers and installers of PV systems, based on the North American Board of Certified Energy Professionals PV Installer certification. A wide variety of training opportunities exist from online courses and free information to hands on workshops and college courses. See www.cansia.ca for more information.

Range of Operational & Maintenance requirements (ex: how much labour time per week for how many people):

Requires only periodic monitoring and maintenance to ensure proper functioning.

Potential problems or challenges:

Currently, cost is the main barrier for grid tied PV systems. Additional challenges include the need for more training opportunities for existing construction professionals and new solar professionals, education for policy and decision makers, appropriate planning and permitting processes. Production incentives, access to favourable financing, tax credits and grants can help make PV an accessible technology.

Other considerations:

Investigate Maintenance contracts or warrantees.
Ensure system is designed for climate and hot water use.
Ensure southern exposure clear of obstructions between the hours of 10 AM and 3 PM or longer.

Permitting:

Check with your local municipal building permitting office regarding required permits. An electrical inspection will be required. Often, local decision makers, grid operators and permit offices are unfamiliar with PV technology or may not have well established guidelines. Education may be required. Be sure to contact your local utility and permit office early in your project development.

Range of warranties and life expectancy of the systems:
Warranties:

PV panels usually come with 20-30 year warrantees. Grid tied inverters usually come with 7-10 year warrantees.

Life Expectancy:

PV panels can be expected to last well beyond the20- 30 year warrantee. Inverters may need to be replaced approximately every 10-12 years.

Solar Resources Assessment:

Site specific solar resources can be measured by visual techniques and inspection or through commercially available solar site analysis tools. The U.S. National Renewable Energy Laboratory has extensive solar radiation resource information at http://rredc.nrel.gov/solar/. Links to Canadian solar radiation data can be found at http://www.canren.gc.ca/resou_asse/index.asp?CaId=55&PgId=452

Canadian Solar Resource maps are available at: http://atlas.nrcan.gc.ca/ and https://glfc.cfsnet.nfis.org/

Inputs and outputs for the technology:
Outputs:

PV panels convert the energy of the sun directly to Direct Current electricity.

Inputs:
Sun:

A southern exposure unobstructed from the hours of 10 AM to 3 PM is preferred.

Electricity:

A very small amount of electricity is used by the inverter. Most grid tied inverters on the market today are 90-97% efficient.

Potential combination with other energy systems (hybrids and combination systems):
Water Heating and Space Heating:

Solar PV panels often get quite hot when operating; however they operate better when colder. A new technology combines PV panels with solar hot water panels to make use of the heat energy absorbed by the PV panels. Drawing the heat into water panels also improves the efficiency of the PV panels. (www.solarwall.com)

Roofing Material and PV:

Some PV panels double as roofing material. If you need a new roof this is a good time to consider PV roofing panels.

Links to other sources of information:

 

Sources of supply (in Canada):

Check CanSIA's website for contact information for suppliers and installers in your area. www.cansia.ca
Énergie Solaire Québec sells for a small fee (free with membership) a list of renewable energy suppliers and businesses in Quebec. http://www.esq.qc.ca/

Recommendations on how to proceed with a project development:

Contact CanSIA: check their database for a local installer.
Finding a contractor: As when hiring any contractor, ask for references from other clients or examples of their work and past experience.
Contact your local building inspector and municipal permitting office.
Ensure you have the necessary permits and the inspector is familiar with your plans before construction.
Contact your local utility
Investigate potential incentives, grants, financing, tax credits and grid connection regulations.
Check the links above for more information.


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Created: 02-18-2008
Modified: 03-31-2008