Solar Power

In BC's Central Interior

You can sell your excess solar energy to BC Hydro. Here is the information.

Solar power systems used to be small and expensive and provided a bare minimum of essential electricity to remote off-grid homes and cabins. That is no longer the case. Technical advancements and mass production have resulted in a dramatic drop in solar module prices. To compare the price between different sized solar modules, divide the price by the number of watts that the module is rated for. This gives you a dollar per watt figure. Solar energy dealers are selling the large solar modules for about 1/3 the price per watt that the big box stores are charging for their smaller modules.

 The electronic components used in solar energy systems are now all computerized high tech marvels. Modern charge controllers use Maximum Power Point Tracking (MPPT) technology to squeeze ever last watt out of a solar array or wind turbine. (The old technology, less efficient charge controllers are still available).

Inverters are much larger than they used to be and now generate 120/240 volt split phase power just like the grid does. Your surplus power can even be sold back to the grid (BC Hydro). (Here is a story about one installation) If your needs grow, additional inverters can be added to the system and they are even available in 3-phase configurations. Old technology inverters are still available in the big box stores but they are intended for portable, temporary use and are not to be installed in homes or cabins.

Solar power systems are available in three basic types, off grid, grid tie without battery back up, and grid tie with battery back up. Solar PV systems are not just for off grid living any more. With the price of grid power rising and solar prices dropping, many people are opting to add solar power systems to their on-grid homes. The cost of BC Hydro's electricity and solar generated electricity are now about the same over the life of a system. However, with rising grid prices, solar will soon be less expensive than the grid. With solar, you have to pay up-front for 20+ years of energy. The low mortgage rates make it attractive to finance a solar power system as part of a home purchase or renovation.

Terminology
The word "panel" has been over used to the point of confusion. To reduce the confusion, solar photovoltaic (PV) units are now called modules and solar thermal units are called collectors. Several modules mounted on a frame as shown in these photos are called an array.

Power is a rate of energy consumption and is measured in watts or kilowatts (1,000 watts). Energy is the power consumed multiplied by the number of hours that you were using it and is measured in kilowatt-hours (kWh). The utility meters on buildings measure energy consumption in kWh. There is no such thing as kilowatts per hour. The word "per" indicates division, not multiplication. 

Solar Trivia
The earth rotates 360 degrees in 24 hours which is 15 per hour or 1/4 per minute. The apparent elevation angle of the sun in the sky changes 23 (from solstice) over the course of a year at a maximum rate of .016 per hour (.384/day). Here at 53 north latitude, the sun's apparent path on the shortest day of the year (winter solstice) is 98 of arc, little more than a quarter of a revolution and rising only 12.7 above the horizon at solar noon. However, on the longest day of the year (summer solstice) the sun rises at 04:40 and sets 17 hours later at 21:42 and the sun's apparent arc is 268 or about 3/4 of a complete revolution and it reaches 60 above the horizon. A total eclipse can theoretically last up to 7.5 minutes.


This is one of several arrays that we installed in 2013. They ranged from from 4 to 16 modules each.

We installed this array of sixteen, 290 watt modules at an off-grid site. Each solar module is about 1m wide by 2m high.

This 4,600 watt array charges a 48-volt Surrette battery using a single Midnite Solar Classic-200 charge controller. The Schneider Xantrex inverter provides 6 kilowatts of 120/240 volt power.

The pole structure was installed by the home owner. The center of the array (top of the poles) is 8.5 meters (28 feet) above ground to prevent shading by the trees during the winter.

The array was assembled on the ground and a crane truck was used to lift the array into position. A bucket truck was used to do the attachment and final wiring.

To save floor space, this bank of Surrette S2-945 (945-ah) AGM cells were installed in a steel rack (AKA battery stand).

Each cell has 4 positive and 4 negative posts and all of them must be connected. We ordered custom plates (straps) to do the inter-cell connections. The alternative would have been a rats nest of 48 separate cables between the cells! The result is a very neat and compact installation.

The front and top safety covers on the battery stand completed the installation.



AGM means Absorbed Glass Mat. They are a starved electrolyte battery similar in concept to the older gel cells but with different construction and characteristics. Like gel cells, they are maintenance free sealed cells with a pressure relief safety valve to allow gases to escape if the battery is severely over charged.
This 1.8 Kw array near Prince George is mounted on a dual-axis tracker so it locks onto the sun's position at sunrise and follows the sun on its daily trip across the sky.  During the summer, in this area, the sun rises behind a stationary array at about 4:00am and sets behind the array at about 10:00pm. We love our long summer days! The tracker enables the array to follow the sun from sunrise to sunset, increasing solar production by up to 8 hours on the longest days of the year.

Array trackers are not cost effective for off grid installations. When an array is sized for winter production, in the summer, it will produce more energy that can be used. With no way to sell the surplus energy produced by tracking the sun, the money is better invested in more solar modules.

This array supplies the power for an off-grid residence that is located a few kilometers north of Prince George.

In this installation, the mounting platform is all treated wood construction. It is located on the side of a south facing hill overlooking the Fraser river. The solar modules are mounted on aluminum frames that are bolted to the platform.


Maintenance free absorbed glass mat (AGM) batteries are more expensive than flooded cells (dollars per kilowatt-hour of energy storage) but they are ideal for remote locations where maintenance is difficult. They are available in various sizes. The 2-volt cells are preferred for larger battery banks. This set of S2-590 Rolls batteries (made by Surrette) is rated at 590 amp-hours at the 100 hour rate

Surrette 927amp-hour batteries used in a 24-volt system near Prince George. These double-walled batteries are suitable for use inside a home. Each of these 6-volt batteries weighs 316 pounds.

(model 6CS25PS)


Surrette.com
 


A small backup power system using solar and wind. This Outback inverter delivers up to 2,800 watts at 120 volts to run the furnace, fridge, freezer, and some lights.

Too bad the photographer  didn't hold the camera level. I'll try to do better next time.
For a large battery, a single string is preferred to connecting smaller batteries in parallel. This set of twelve Surette/Rolls S-1390 cells forms a 24-volt battery rated at 1,390 amp-hours.

An older system using a pair of Trace 1,500 watt modified square wave inverters for 120/240 vac power. This equipment is 3 generations old but it's still doing the job.


This system has been upgraded by replacing the original solar charge controller with an Outback maximum power point tracking (MPPT) unit. The array was then re-configured to operate at twice the battery voltage, reducing power loss in the cables to 1/4 its previous value.