Solar 101

The Design process for an on-grid system is very different than that of an off-grid system. An on-grid system typically does not have batteries and certainly does not require batteries except in case of a grid-outage. An off-grid system requires an in-depth knowledge of the electrical loads and battery maintenance by both the installer and the customer. In general, off-grid systems require more planning, consultation, and industry knowledge, they are also more expensive (mainly due to the cost of the batteries) and often require more existing infrastructure such as non-electric heat sources or hot water sources.

The design process for a grid-tied system is relatively simple, as the installer does not need to know what the electricity is being used for. A grid-tied system also does not need to meet the entire electrical demand of the property. Most installers use satellite imagery and your historical annual kWh usage (commonly found at the bottom right hand side of your NSP bill) to determine how many panels can fit on the roof or ground and what the production will be for that size of system.

Solar energy is radiation from the Sun that is capable of producing heat, causing chemical reactions, or generating electricity. There are a variety of ways in which the sun's energy can be harnessed including;

Solar Photovoltaics (PV) generates electricity. Solar panels produce DC (Direct Current) power which then needs to be inverted to AC (Alternating Current) to be used by your house and the grid, or fed directly to a battery bank in the case of an off-grid system. Solar PV is the dominant form of solar technology and most of these questions are geared towards Solar PV.

Solar Hot Water uses heat from the sun to heat up and circulate water.

Passive Solar is a building practice that utilizes the sun in passive ways. Skylights and sun tunnels are examples of passive solar design. Another example would be large south facing windows with an overhanging roof such that the house is heated by the sun when it's lower in the sky in the winter and cooled by the overhang when the sun is higher in the sky in the summer.

Why use solar energy?

Solar Energy is a renewable and plentiful resource that has few limitations. Harnessing solar energy is comparitively cheap and the energy produced can be used directly at the source as opposed to traveling great distances. The two main limitations are shading from nearby trees (nature's solar panels), and that the sun is an unreliable generator, meaning solar production/effectiveness is heavily skewed towards summer months. Net-Metering or the current Self-Generation Offset program allows a grid-tied home to produce power which feeds the house first, any excess power is then sent to the grid which is recorded by a bi-directional meter. This meter will provide credits that can be used at night and after a summer's worth of production you can offset the winter's use as well. A more detailed explanation on Net-Metering and the Self Generation Offset Program can be found here(link!) A Net-Metered Solar PV system uses the grid as an "infinite battery bank", where your excess summer production can be banked for winter.

Some parts of a solar installation can be done by anyone, but anything involving electricity should be handled by an electrician. Both on and off-grid solar PV systems need to be installed by a Red Seal electrician and inspected by Nova Scotia Power or the local electrical inspectors.

In general, racking and mounting panels, building a ground mount frame (depending on local building code), trench digging (if required), can all be done by someone with the skills and safety equipment/certifications to do so.

A Solar PV system is capable of producing more power than your property uses in a day, this excess goes back to the grid. During a power outage you cannot export power to the grid as it could injure line-workers so all grid-tied Solar PV systems are designed and required to shut down automatically as soon as they stop detecting the grid. This is called "anti-islanding". Additional components can be installed that allow a part or all of a grid-tied solar PV system to operate during an outage but this typically requires a significant investment and is not trivial.

A Solar PV system will last as long as it's component parts do. Solar PV Systems can broadly be broken down into 3 categories, each with varying warranty lengths.

Solar Panels Solar Panels have two types of warranty. Linear Output (a.k.a production warranty) and Product Warranty. Solar Panels degrade over time as they get damaged by the sun and as they degrade their output decreases. A typical degradation rate is 15% over 25 years. A linear output warranty allows for a replacement panel if the panel starts producing less than it's expected to - most linear output warranties are 25 years. Although rare, a panel ceasing to function entirely would be covered by product warranty, which are typically 10+ years. Although panels degrade over time, a system's performance should not noticably decrease over 25 years if the panels are a higher wattage than the inverter(s) which is a fairly standard practice.

Inverters Inverters take DC power produced by the solar panels and convert it to AC power to be used by your house and the grid. There are different types (string or central inverters and micro-inverters), each with their pros and cons, and varying costs and warranty lengths. Efficiency Nova Scotia recommends an inverter warranty of at least 10 years.

Racking

Roof Mounted racking is typically aluminium and most types carry at least a 20 year warranty. Ground mounted frames are typically galvanized steel or concrete ballast. Generally speaking, roof mounted racking is rated for higher wind loads than ground mounted frames because most roof mounted racking is not tilted up at an angle away from the roof.

In general, a solar PV system is expected to last 25 years, and potentially much longer.