Although the concept of using the energy from the sun to generate electricity has been understood and developed for decades, until recently the only practical way to ensure a 24 hour supply of electricity was to store that energy in batteries for subsequent use. This was fine, albeit expensive and complicated, for folk living ‘off the grid’ or where it was prohibitively expensive to get Hydro power to the site.
In recent years it has become possible to use the supply authority’s grid as a virtual battery, by way of taking electrical current into the house through the meter when needed, but also sending power generated on site back to the grid when the panels are generating more than the house is consuming thus effectively running the meter backwards.
There is a problem in as much that if more than approximately 20% of the grid’s capacity is sent ‘back’ by end user generators, the switching and control systems that monitor the local grid will fail. These were after all, mainly designed long before the Net Metering concept. So supply companies in some areas such as Hawaii are having to cease their Net Metering agreements while they come to terms with the problems this causes.
HESPV, one of the leading suppliers of solar PV related equipment in Canada recently published a study “The Case for Residential Solar Electricity in Canada 2014” which can be downloaded by clicking on the link.
Since we are specifically talking about Fortis BC’s Net metering system here, perhaps a few details are in order.
Fortis BC announced in 2009 that it had proposed to the BC Utilities Commission , and had had accepted by them, a proposal to allow small ‘self generators’ to attach to their system, to a maximum of 50kW of generating power. This limit was seen as a reasonable ‘boundary’ between home owners wishing to lower their bills and dependency on Hydro, and other commercial generators. The so called ‘Independent Power Producers’.
Since then approximately 100 small ‘self generators’ have applied to join the scheme, and it appears that with a couple of larger exceptions, most are families with 40 or fewer panels. Most panels at this point are 250w, so a 40 off 250w panel scheme is capable of generating a maximum of 10kw in optimum conditions, although static panels even when directly oriented at the mid day sun are considered to be only about 71.1% efficient, and the inverter used also makes a difference.
From FortisBC’s own website:
“Under the simplest version of net metering, there is a single meter that runs backwards when the generator produces more electricity than the customer requires and runs forward when the generator produces less than the customer requires.
Customers are only billed for their positive “net consumption”, which is defined as their total consumption minus their total generation in a given billing cycle, as shown by a positive meter reading.”
To be continued…