ENERGY
MATERIALS ENCYLOPEDIA
Energy intro
In the short space of a century, electrical energy has gone from a rare novelty to an absolute necessity. Rare is the homeowner that does not envision some form of electrical power in their building. For lighting, heating, refrigeration, communications or work-reducing appliances, electrical energy is ubiquitous in our homes. It has proven to be an abundant and affordable source of power, the likes of which have never been experienced on the planet. Homeowners wishing to make use of electrical energy have three major sourcing options to meet their power needs.
Grid Power
Most homeowners receive their energy from public or private utility companies, whose large, centralized generating stations produce high volumes of energy that are distributed through a network of transmission lines that connect almost every home and business in North America and has come to be known as “the grid.”
The infrastructure of the electrical grid is vast. It is a rare and uninhabited place in North America where some visual sign of the electrical grid is not present. The energy on the grid is carefully monitored and controlled from point of generation to end user.
There are many kinds of electrical generation on the grid, including:
Hydroelectric — The power of falling water is used to spin turbines that generate electricity.
Fossil fuel plants — Heat from the burning of fossil fuels (including coal and natural gas) is used to create steam that is used to spin turbines that generate electricity.
Nuclear plants — Heat from the fission of atoms is used to create steam that is used to spin turbines that generate electricity.
Wind turbines — The power of wind is used to spin turbines that generate electricity.
Solar thermal — The heat of the sun is concentrated and used to create steam that is used to spin turbines that generate electricity.
Photovoltaic — Photons from the sun are used to displace free electrons on a silicon wafer to generate electrical current.
Regionally, different balances of these sources make up the overall available energy. It is impossible for a homeowner to know the exact source of the electrical energy being used in the home. Proximity to a particular generating station is some indication, but it is the nature of the grid that it is impossible for the homeowner to predict power flow.
Most of the electrical power on the grid is generated by means that have major, well-documented environmental impacts. Centralized production is also extremely inefficient, with overall losses in production ranging from 30–70 percent and transmission losses around 8 percent, which means that only a fraction of the energy value of the fuel being used is actually making it to the end user.
A small number of private utility companies offer homeowners a means of “purchasing” 100 percent renewable energy from the grid. Under these programs, the amount of electricity used by a homeowner is put onto the grid by the private utility, offsetting the need for that amount of “dirty” power to be generated.
Grid-Tied
The grid has always been a two-way power highway; electrons will move from a point of generation to a point of consumption in either direction along a wire. Until quite recently, utility companies treated the grid like a one-way street running from central production facilities to end users. In recent years, the value of “distributed generation” has become evident and many utilities have begun to allow for small-scale production by homeowners and businesses, often under direction from governments.
“Grid-tied” homeowners and businesses produce power (typically with renewable sources like photovoltaic, wind and small-scale hydro) under a variety of different contracts and terms. Generated power is put onto the grid and the owner of the generator receives money or credit for that power. If the owner also requires electrical power, it is supplied from the grid. In this way, a homeowner can become a “net-zero” electricity user, generating as much power as he or she uses.
These grid-tied systems offer numerous benefits to both homeowners and utility companies. Homeowners can provide for a desired portion of their own electrical needs (from a small percentage to overproduction for profit), yet not be reliant on having to store and manage their own power supply, as would be necessary for off-grid systems. Renewable sources like solar and wind produce a lot of power sometimes and no power at other times. With the grid as a “buffer” the home is never without power when needed. Utility companies benefit from having homeowners and businesses put out the investment for new production that can collectively offset the need for expensive new large-scale generating capacity and increase the percentage of clean renewable energy in their mix.
Distributed generation helps to reduce the high production and transmission losses associated with centralized power plants by reducing the distance from point of production to point of use, and creates a more resilient grid less susceptible to massive outages when a large power plant goes offline.
Off-Grid
A much smaller number of homeowners generate and manage their own electrical energy, functioning independently in “off-grid” homes. These systems typically rely on a bank of batteries that provide chemical storage of electrical energy, which can be charged by the home energy system as power is available and drained when power is required in the home.
Off-grid systems reward energy-efficient home design and conservative power use within the home. If energy demands are low, this type of system can be affordable and reliable. As demands rise (and most North Americans demand much more power than is practical to supply in an off-grid system), the systems grow in size, complexity and cost.
The addition of battery storage, off-grid systems require the homeowner to house and maintain batteries and associated controls and ensure the balance of power in and out of the system.
Off-grid systems are typically much larger than grid-tied systems, to accommodate the variable nature of renewable energy, where daily and seasonal swings in generation can require overproduction and large storage capacity of power is to be available through times of low or no production.
Off-grid systems provide a high degree of independence and resilience, with little or no reliance on outside sources of production or delivery.
Only renewable forms of electrical power generation will be considered in the sub-pages of the ENERGY section