Many people have asked us why we are installing solar photovoltaic panels on our roof. They believe that solar thermal panels are superior since solar thermal can provide hot water for (1) domestic hot water; (2) radiant heating inside the house; and (3) heating the swimming pool.
Since we will have geothermal energy available for our domestic hot water, heating in the house, and even to heat our swimming pool, we have a greater need to generate electricity.
Our geothermal heat exchange uses multiple pumps. These pumps need electricity to operate, so we will be using renewable energy from our photovoltaic panels to obtain renewable energy from the earth.
Our stated objectives include being zero net energy and zero carbon. We intend to meet these objectives is through renewable resources, including geothermal heat exchange and solar photovoltaic generation.
Increasing Use of Electricity
Generally, our household has been an early adopter of new technologies. These technologies often require electricity to operate. Thus, our household may use more electricity that others so we want to be ‘hedged’ against the rising cost of electricity.
In an article today entitled, ‘Plugged-In Age Feeds a Hunger for Electricity ‘ the New York Times reported that:
Worldwide, consumer electronics now represent 15 percent of household power demand, and that is expected to triple over the next two decades, according to the International Energy Agency, making it more difficult to tackle the greenhouse gas emissions responsible for global warming.
To satisfy the demand from gadgets will require building the equivalent of 560 coal-fired power plants, or 230 nuclear plants, according to the agency.
To reduce the burden that our household will put on the grid, we’re going to to two things.
First, we will do our best to anticipate where ‘always on’ devices will be and have ‘on/off’ switches in those locations. These switches may be connected to our home automation system so the switches can be turned off automatically when required.
Second, we’re going to have solar photovoltaic panels on our roof.
Sizing Our Photovoltaic Panels
We designed our house so we could fit up to 48 solar photovoltaic panels on the roof. However, due to the current legislation in California, we can only generate as much electricity as we use. We cannot be net generators of electricity. Frankly, we can’t understand this legislation and we believe the legislation needs to change. This issue is in front of the California senate, with AB 560 (to raise the limit on net metering from 2.5% to 10%) and AB 920, which would allow homes to be net generators of electricity.
Existing law provides that where the electricity generated by the eligible customer-generator exceeds the electricity supplied by the electric distribution utility or cooperative during a 12-month period, the eligible customer generator is a net electricity producer and the electric distribution utility or cooperative retains any excess kilowatthours generated and the customer-generator is not owed compensation for those excess kilowatthours unless the electric distribution utility or cooperative enters into a purchase agreement with the eligible customer-generator for those excess kilowatthours.
Given the size of our house and usage patterns, Akeena Solar estimated that we should install 32 photovoltaic panels and that will drive our consumption to zero. Given that the cost of photovoltaic panels is dropping and the performance is increasing (and, we simply can’t generate a financial return on additional photovoltaic panels), we’re limiting our installation to 32 photovoltaic panels.
We will, however, have all the infrastructure in place to support 48 photovoltaic panels so when the legislation changes and we can be a net generator of electricity or, if our power consumption is greater than expected and we need more panels to drop our net consumption of electricity to zero, we can simply bolt in the additional photovoltaic panels as and when required.
Future Capability for Electric Vehicles
Although we do have electric vehicles today, we are going to have our garage wired for charging electric vehiclces. If we have electric vehicles in the future (Tesla?) then our consumption will increase. And we’ll simply bolt in those additional photovoltaic panels.
To help heat our swimming pool, we plan to put PEX tubing in the concrete decking around the pool. Thus, the warm pool deck will pre-heat the water circulating in the pool, which will heat the pool and cool the deck. With appropriate valves and controls, this should be a win/win.