Battery Back Up

You should look at other options for back up power

In a previous post I promised to write about Battery Back Up.  I will do so now. In future monthly postings, I will choose topics and do some research to bring in interesting ideas. In these initial posting  I am using my mental database as my only resource as I am trying to “prime” the blog.

Other Options

You should look at other ways to obtain emergency power. Many homeowners choose gas generators  as the right size gas generator can run the entire house. Running your whole house as usual on batteries is an enormous task because batteries drain quickly when large loads are connected to them. When we design a system, we must ask numerous questions of the homeowner.  We must find out what are the essential loads to be backed up. Our electrician must install a pony panel and to run the necessary wires so that when the grid goes down, power from the storage battery flows only to the selected loads.

Select Loads to be backed up

Typically, homeowners choose furnace motor, fridge, some lights, an outlet for plugging in a computer and any essential medical appliances.

How Many Hours must battery last?

Decide how many hours the selected loads must be powered. With that information and loads, we can estimate how many kWh of storage to provide.

Sun  shining on the panels will add to autonomy once the batteries are charged but in our climate most outages occur during the winter when sun hours are few or panels covered with snow and ice.

None of this is cheap – adding a pony panel and batteries can double the cost of a net metered system.

 

Shading of the Solar Array

Include a shade analysis when doing a site assessment.

Shadows reduce solar production

Passing shadows  reduce the productivity of a solar array. Shadows are cast by trees, buildings, passing clouds, falling leaves….but we love trees!

If there are shading concerns, we include in the site assessment an analysis using a “Sun Eye” or similar device. Its report will accurately forecast the monthly energy shortfall.

Nowadays most central inverters have 2 inputs so at worst half of the array would be affected until the shadow passes.

We recommend micro inverters or Optimizers to minimize loss when shading is an issue.

Both maximise the efficiency of individual panels by their MPPT technology. (Maximum Power Point Technology).

Optimizers are small devices attached to every solar panel in the array and have the effect of bi-passing the affected panel or panels so that the remainder of the array is not affected by the shadow. 

In some cases just a few optimizers can be placed on modules directly affected by shading.

Optimizers are usually  more cost effective than microinverters.

Central Inverters at ground level teamed with optimizers on the roof reduce the need for workmen to climb on the roof, saving wear on shingles.

Micro- inverters and optimizers both perform the additional function of maximizing production of the individual solar panel by their MPPT algorithms and can add 5% productivity to any array even without shading. They both  provide web based monitoring of individual panels and useful reports.

Its addictive to view either on line display to see how the show on your rooftop is displaying and to compare production between months or years.

We have had good results using Solar Edge Central Inverters with Optmizers. Here’s a link to their website:

www.solaredge.com/us/

The original microinverter is Enphase. Here’s that link: www.https://enphase.com/en-us/residential-solutions

Either solution brings more on line fun than plain vanilla reports from central inverters can provide as the homeowner can view on line how each solar panel is functioning.

 

Energy Storage

Energy Storage is a hot topic nowadays. In Europe and some USA States, where homeowners are charged time-of-use rates, it makes sense to invest in a battery to store solar electricity for  use at times when the rate charged per kilowatt hour is highest.

In Ontario, once the grid connection is changed to net-metered, the smart meter is removed and the customer is charged a flat rate so the rate charged  is no longer affected by time of use.

Ontario customers at this point in time do not need a battery for energy storage as a net-metered connection allows consumers to use the grid as their battery.

Back-Up power is an entirely different issue. I will discuss battery back-up in my next post.