Kinark Sustainable Living Centre

Electrical System

We tend to take electrical systems for granted in our built environment, and rarely consider where the power comes from or how it’s delivered to us because it’s done so fairly invisibly. From obvious uses like lighting to more hidden uses like water pumping, modern buildings don’t function without electricity. But how much do we really need, and by what means should we obtain it?

Design Intent

1. To use only as much power as can be affordably generated and stored on site
2. To expose the electrical system so power can be traced from source to device
3. To use as little electricity as possible, and to have building users be mindful of this fact
4. To house the electrical system outside the main building to highlight its components

Methods and Materials

This building operates with an off-grid (ie, no connection to the hydro utility lines), photovoltaic system. Photovoltaic panels (often called “solar panels”) turn sunlight into direct current (DC) electrical energy. This energy is stored in large batteries. When the building needs electricity, the DC energy stored in the batteries goes through an inverter, which changes it to alternating current (AC) electrical energy, to mimic that of the utility grid. This energy is supplied to the lights, water pump, heating system and other electrical devices as needed. A monitor in the power shed keeps users informed of the amount of power available in the batteries at any given time. The system was designed to use the minimum amount of generating capacity (approx. 500 watts) and storage capacity (800 amp hours) required to service the building.

Questions

What happens to the solar electrical system on cloudy days and at night?

During the daytime, enough energy should be stored in the batteries to provide continuous power to the building on cloudy days and at night. It is possible to run short on power, especially during long cloudy periods in mid-winter, when very little sunlight is available.

What happens if there’s not enough power?

It would be very rare for there to be so little power stored in the batteries that the building cannot function. The building’s users must adapt and adjust their demands according to the power that is available at any given time.

What happens if there’s a power outage?

If the main hydro utility goes off-line, this building will be unaffected.

Is solar energy expensive?

It is difficult to quantify this answer. With utility power, you get your lifetime supply of electricity on a “payment plan” that divides the cost up over the entire time of use. While the price of utility power may seem low per Kilowatt hour used, it comes with many additional charges that must be accounted for. With a renewable energy system like this one, you pay a one-time, up-front cost for your power, and then have access to that power for the lifetime of the system. Whether or not it is more or less affordable will depend on your power usage; the more you require, the steeper the initial price for renewables.

Why solar power and not wind, or a combination of the two?

Wind power was not chosen for this building because of siting difficulties. In order to put a wind turbine in clean, undisturbed air a very tall tower would have to have been constructed in order to be clear of the surrounding trees. The cost of such a tower would have been outside the budget for the project. Wind speeds in this area are not reliably charted, making it a risky investment in a densely treed area.

How long does a system like this last?

Most of the components of this system will last at least a generation. The PV panels are warrantied for 25 years, and the inverter and other switching gear have lifetimes similar to other conventional electrical system components. The most variable lifespan will be for the batteries. If they are treated well (not drained too often, kept well charged) they can last up to 15 years. Poorly treated, they may need replacing in 5-10 years. Again, the key to a successful off-grid system is monitoring your energy demands and adjusting them to suit the amount of power available.