How solar water heating works
Solar collectors trap heat in the same way a car’s interior does when it sits in the sun. Water or anti-freeze is pumped through tubes in a collector and heated. This energy is then transferred thru a heat exchanger and stored as potable water in a solar storage tank. This solar heated water is fed directly to your hot water heater or furnace, ensuring the sun is your first source of heat and minimizing the amount of gas/electricity needed.
By adding panels and another heat exchanger, solar heated water can also assist radiant floor systems or traditional forced air furnaces. An additional thermostat is added to ensure the sun is the first source of heat for your home and a relay switch converts your furnace to a hybrid heater, further reducing the need for natural gas or other fuel sources.
Types of collectors
Flat plate collectors are highly insulated, aluminum framed boxes covered by tempered glass. Inside, heat is collected by absorber fins, reflectors or concentrators. Flat plate collectors are the most common collector type and efficiently heat a high volume of water to a medium temperature (generally up to 180 degrees).
Evacuated tube collectors are usually made of parallel rows of transparent glass tubes. Air is removed, or evacuated, from the space between the two glass tubes to form a vacuum, which eliminates conductive and convective heat loss. These collectors heat a lower volume of water but to higher temperatures.
Outdoor swimming pools make use of relatively inexpensive unglazed collectors made of UV resistant plastic. Pool collectors hook right up to the pool’s existing filter pump. They can deliver up to 100% of a pool’s heat from Memorial Day to Labor Day in Illinois and are one of the most cost-effective applications of solar energy.
Solar Electricity (Photovoltaics)
Photovoltaic (PV) solar panels use semiconductor materials to convert sunlight directly into electricity. Simple solar cells power watches and calculators while larger arrays provide energy for homes, businesses and even cities.
The sun’s photons strike the solar panel, dislodging electrons and creating a direct current (DC) which is converted by an inverter to the standard “alternating” current (AC) and then delivered to the home. Although a relatively young technology, major advancements are underway to improve the efficiency and therefore the economics.
Systems are silent, produce no emissions, and operate during the highest daytime electrical demand. PV cells are guaranteed by the manufacturer for decades as there are no moving parts and the panels are very durable.
Newer PV products can now also double as roofing or building materials called Building Integrated PV (BIPV). These products can be more aesthetically pleasing and serve the dual purpose of protecting the building from weather while generating electricity. These materials are typically less efficient but offer many opportunities for advancement.
Renewable Energy Basics (click on the legend icon to learn about each technology)
Solar Thermal Systems
Solar Thermal technology has been used for thousands of years to heat water and/or homes, keeping families comfortable and warm. In fact, Davinci used solar thermal concepts to heat the Roman Baths! There are over 60 million solar water heating systems in the world, with thousands in Illinois.
Solar water systems are easily integrated into your existing hot water heater, forced air furnace, radiant floor boiler and pool heating systems. They utilize reliable and proven technology to provide decades of worry-free, clean energy. Solar hot water systems are commonly required for new construction in many parts of the world including Hawaii because of their highly efficient and cost effective design for providing hot water naturally.
Solar thermal minimizes rising and volatile energy costs while reducing pollution and reliance on natural gas, an increasingly imported source of energy. Systems cost little to run and last decades with minimal maintenance. They have a strong return on investment and compare in added home value to a kitchen remodel or the addition of a deck.
Types of PV Systems
Utility Grid Interconnected - Also known as “on-grid” or “grid-tied,” these systems tie directly to the utility grid so there is no need for battery storage. If the PV system generates more electricity than the owner uses, excess electricity is sold back to the power company - spinning the electric meter backwards! The building will need to buy electricity from the grid during nighttime or cloudy periods.
Off-Grid or Independent - Operates independently of the utility grid by utilizing batteries for storage. This is typically more expensive and requires additional maintenance.
Grid-Tied with Battery Backup - Also called “bi-modal,” this system ties into the utility grid but also uses batteries for backup, which protects against power outages.
As with any heat pump, geothermal and water-source heat pumps are able to heat, cool, and, if so equipped, supply the house with hot water. Some models of geothermal systems are available with two-speed compressors and variable fans for more comfort and energy savings. Relative to air-source heat pumps, they are quieter, last longer, need little maintenance, and do not depend on the temperature of the outside air.
A dual-source heat pump combines an air-source heat pump with a geothermal heat pump. These appliances combine the best of both systems. Dual-source heat pumps have higher efficiency ratings than air-source units, but are not as efficient as geothermal units. The main advantage of dual-source systems is that they cost much less to install than a single geothermal unit, and work almost as well.
Even though the installation price of a geothermal system can be several times that of an air-source system of the same heating and cooling capacity, the additional costs are returned to you in energy savings in 5-10 years. System life is estimated at 25 years for the inside components and 50+ years for the ground loop. There are approximately 50,000 geothermal heat pumps installed in the United States each year.
Level 1 equipment provides charging through a 120 volt (V), alternating-current (AC) plug (up to 15 amperes and 1.8 kW). Level 1 EVSE is portable and does not require installation of charging equipment. On one end of the cord is a standard, three-prong household plug. On the other end is a connector, which plugs into the vehicle.
Level 1 works well for charging at home, work, or when there is only a 120 V outlet, or "trickle charge," available. Depending on the battery type, Level 1 charging can take 6 to 20 hours for a fully depleted battery to reach a full charge, adding about 2 to 5 miles of range per hour of charging time, depending on the vehicle.
Level 2 equipment offers charging through a 240 V, AC plug and requires installation of home charging or public charging equipment. This charging option can operate at up to 80 amperes and 19.2 kW. However, most residential Level 2 EVSE will operate at lower power. Many such units operate at 30 amperes, delivering 7.2 kW of power. These units require a dedicated 40 amp circuit.
Most homes have 240 V service available, and because Level 2 EVSE can easily charge a typical EV battery overnight, this will be a common installation for homes. Level 2 equipment also uses the same connector on the vehicle as Level 1 equipment. Based on the battery type and circuit capacity, Level 2 charging can take 3 to 8 hours for a fully depleted battery to reach a full charge, adding about 10 to 20 miles of range per hour of charging time, depending on the vehicle.
Level 3 charging will enable a faster AC charging option. Level 3 equipment is still in development. This charging option will operate at a higher voltage and current than Level 2, and it would be installed at public charging stations. Level 3 charging could take less than 30 minutes to reach a full charge.
DC Fast Charging
Direct-current (DC) fast charging equipment (480 V) provides 50 kW to the battery. This option enables charging along heavy traffic corridors and at public stations. A DC fast charge can take less than 30 minutes to fully charge a depleted battery, adding 60 to 80 miles of range to a light-duty PHEV or EV.
Inductive charging equipment installed for all-electric vehicles in the early 1990s, such as the Toyota RAV4 EV and the Chevy S10 EV, is still being used in certain areas. Some companies are working on inductive charging options for future electric drive vehicles.
Connectors and Plugs
Modern charging equipment and vehicles have a standard connector and plug receptacle. This connector is based on the Society of Automotive Engineers (SAE) J1772 standard. Any vehicle with this plug receptacle can use any Level 1 or Level 2 EVSE. All major vehicle and charging system manufacturers support this standard, which should eliminate drivers' concerns about whether their vehicle is compatible with the infrastructure. The DC fast charging connector has not been standardized yet. To receive DC fast charging, most EVs and PHEVs are using the Tokyo Electric Power Company (TEPCO) connector and receptacle, which have not become standard yet. Manufacturers may offer the TEPCO DC fast charge receptacle as an option on vehicles until a standard is in place.
When the wind spins the wind turbine's blades, a rotor captures the kinetic energy of the wind and converts it into rotary motion to drive the generator. The manufacturer can provide information on the maximum wind speed at which the turbine is designed to operate safely. Most turbines have automatic overspeed-governing systems to keep the rotor from spinning out of control in very high winds.
A small wind system can be connected to an electric distribution system (grid-connected) or it can stand alone (off-grid).
See our wind power animation for more information.
With proper installation and maintenance, a small wind electric system should last up to 20 years or longer.
Before installing your system, you first need to do the following:
• Find the best site
• Size your wind turbine
• Decide whether you'll have a grid-connected or stand-alone system
• Understand your local zoning, permitting, and neighborhood covenant requirements.
Small Wind Electric Systems
Small wind electric systems are one of the most cost-effective home-based renewable energy systems. These systems are also nonpolluting.
If a small wind electric system is right for you, it can do the following:
• Lower your electricity bills by 50% - 90%
• Help you avoid the high costs of having utility power lines extended to a remote location
• Help uninterruptible power supplies ride through extended utility outages.
• How a Small Wind Electric System Works
• Wind is created by the unequal heating of the Earth's surface by the sun. Wind turbines convert the kinetic energy in wind into clean electricity.
Electricity can be used to power all-electric vehicles and plug-in hybrid electric vehicles directly from the power grid. Vehicles that run on electricity produce no tailpipe emissions. The only emissions that can be attributed to electricity are those generated in the production process at the power plant. Electricity is easily accessible for short-range driving.
Charging equipment for plug-in hybrid electric vehicles (PHEVs) and all-electric vehicles (EVs) is classified by the maximum amount of power in kilowatts (kW) provided to the battery. Charging times vary based on how depleted the battery is, how much energy it holds, the type of battery, and the type of EVSE. The charging time can range from 30 minutes to 20 hours or more, depending on the type of charging equipment used.
Geothermal Heat Pumps
Geothermal heat pumps (sometimes referred to as GeoExchange, earth-coupled, ground-source, or water-source heat pumps) have been in use since the late 1940s. Geothermal heat pumps (GHPs) use the constant temperature of the earth as the exchange medium instead of the outside air temperature. This allows the system to reach fairly high efficiencies (300%-600%) on the coldest of winter nights, compared to 175%-250% for air-source heat pumps on cool days.
While many parts of the country experience seasonal temperature extremes from scorching heat in the summer to sub-zero cold in the winter a few feet below the earth's surface the ground remains at a relatively constant temperature. Depending on latitude, ground temperatures range from 45 degree F (7degree C) to 75 degree F (21 degree C). Like a cave, this ground temperature is warmer than the air above it during the winter and cooler than the air in the summer. The GHP takes advantage of this by exchanging heat with the earth through a ground heat exchanger.
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