Systems

Electricity

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Introduction

Canadian households are each responsible on average for 2.5 tonnes of green house gas (GHG) emissions from a combination of heating needs and electrical consumption. Each household also creates another 2.5 tonnes of GHG through transportation. That's five tonnnes for each home, each year.

In the Ontario context, over 20% of electrical production is from coal-fired facilities, which makes electrical use a highly polluting activity. Clearly, it is imperative that we start employing new and reliable sources of electricity. It all starts at home.

Where to Start - Reduce the Demand

When considering an alternative energy system, it is important to start by looking at the demand side of the equation. It's a classical engineering approach to see how you can render efficiencies at the end point of a mechanical or electronic system. The builders of HomeAlive looked at all the energy needs of the home and identified all the possible ways of reducing the electrical demand before actually developing the generating system.

Home Alive was designed with highly efficient heating and cooling systems, well-insulated walls, solar hot water (for domestic use and heating), Energy Star™ rated appliances, natural lighting, and compact fluorescent bulbs.

Overall demand was reduced from the outset, without compromising on the conventional comforts of the home. HomeAlive occupants have all the same creature comforts: washer, dryer, dishwasher, fridge, heat, computer, hot water, etc.

After the demand equation was addressed, a reasonably small alternative energy production system was selected to provide a significant portion of the residents' electrical needs.

Next Step - Wind and Solar

Home Alive incorporates a wind turbine rated at 1.2kW during ideal wind conditions and photovoltaic laminates capable of outputting another 900W in full sun. At its optimum peak, the 2.1kW potential of this system still only represents approximately half the daily consumption by an average household. However, given the choice of appliances and lights (and the residents conscientiousness) in its first few winter months of occupancy Home Alive used only an average of 1kWh more/day than it produced. This amounts to only about 10 cents a day at the 2005 average utility bill rate of $0.10 .kWh.

The wind turbine sends alternating current (AC) to Home Alive This current is easily transmittable over long distances but cannot be stored. Therefore, this is passed through a rectifier to create direct current (DC) from the AC current. If not used immediately by the inverter, this energy can be sent to the batteries for storage.

The photovoltaics on the other hand, generate DC power from the beginning, so it simply bypasses the rectifier and goes straight either to the inverter or the batteries.

Generation and Demand - A Good Balance

While Home Alive's system utilizes batteries that are capable of supplying back-up power when its production is less than the house's needs, a grid inter-tie will first automatically make up the difference between production and need.

Generally in the winter, when there are short daylight hours, the batteries may start to lose their charge. In this case the grid inter-tie automatically recharges the batteries to ensure a topped up charge.

On sunny and/or windy days when the alternative energy system produces more energy than the house requires, it is automatically sent to the grid and spins the electrical meter backwards! This provides a billing credit for energy produced but unused within Home Alive.

During very strong steady winds, production is so high at moments that the inverter cannot convert the incoming power rapidly enough to make full use of it. If the batteries too are full and cannot accept a further charge then this excess peak power is diverted to a 2k ohm resistor, which expends the energy as heat, like an old baseboard electric heater.

With home systems that combine solar and wind energy, the need for governments to increase power production through coal, nuclear or hydro can almost be eliminated. Economically, it is within the reach of all homeowners to convert to some of these new technologies. Environmentally, it is in the interest of everyone and all level of governments to encourage their adoption.

For More on Alternative Energy

• Learn about the HomeAlive systems hands-on. Everdale offers seasonal workshops on different aspects of the systems. You can also take part in guided Saturday Tours of HomeAlive. Visit www.everdale.org
• Check out the HomeAlive Buyer's Guide for suppliers and equipment of these systems.

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