Distributed Generation

Businesses and communities across the Midwest are turning to distributed generation for clean, efficient power - when and where they need it.

• How it works
• Technology
• Applications
• Benefits
• Learn more

If your organization is interested in alternative energy sources, Alliant Energy's distributed generation team can provide expert assistance.

Learn more about generating your own power with our guide to Homegrown Power. [PDF]

Download IPL's Version of the State of Minnesota Proposed Interconnection Process for Distributed Generation Systems (IPL DRAFT)
[PDF format - 74 pages, 2.5MB]

How it works

Distributed generation (DG), also called distributed resources (DR), describes smaller-scale power generation or storage located close to where the power is needed.

Units can be connected directly to the consumer or to a utility's transmission and distribution system. Distributed generation can provide standby generation, peak shaving capability, baseload generation or cogeneration.

Capacity ranges from one kilowatt (the approximate demand for a residential customer) to 15 megawatts to supply large commercial or medium industrial facilities.

Technology

Various technologies are used for distributed generation, including wind and solar power, external combustion engines and “combined heat and power” generators.

Microturbines

These compact generators - not much bigger than a standard refrigerator - use a small jet engine to produce clean, secure, premium power right on your site.

The Capstone MicroTurbine, available from Alliant Energy, provides electrical power up to 30 kW using a compressor, recuperator, combustor, turbine and permanent magnetic generator.

Microprocessors allow the microturbine to vary voltage and power factor as needed. Exhaust gases have sufficient heat to be used for combined heat and power applications.

Microturbines can be configured to use a number of fuels, including natural gas, propane, liquid diesel or kerosene, or methane biogas.

In addition to fuel flexibility, microturbines feature low emissions, significantly reduced noise levels and virtually no maintenance requirements.

Fuel cells

A fuel cell is an electromechanical engine that harnesses the energy released when hydrogen and oxygen combine. Fuel cells produce almost no pollutants and have no moving parts.

In principle, a fuel cell operates like a battery. However, a fuel cell never runs down or requires recharging - it will continue producing heat and electricity as long as fuel is supplied.

The hydrogen needed for reaction in a fuel cell is produced from hydrogen-rich fuels such as natural gas, propane or methane. These gases are run through a fuel “reformer” that converts it to hydrogen and carbon dioxide.

Because fuel cells are a new technology, costs can be prohibitive, but prices are expected to lower as the technology is refined.

Stirling engines

The Stirling engine, also known as an “external combustion engine” was originally patented in 1816 by the Rev. Robert Stirling as “A New Type of Air Engine with Economizer.”

Combustion, in the form of a steady flame similar to a pilot light, takes place outside of a sealed chamber or cylinder. Power is derived from heating and cooling natural gas, propane or diesel fuel inside the sealed chamber with a piston.

When the gas is heated, it expands and builds pressure, pushing the piston out. When the gas cools, it contracts and pulls the piston back in.

The “economizer,” now known as a regenerator, stores heat between the hot and cold cycles.

Stirling engines are about 90 percent efficient, producing about 6,000 watts of heat for hot water and 700 watts of AC electricity. Stirling engines are also available in DC units for remote applications.

Wind turbines

Wind turbines convert the kinetic energy of the wind to mechanical power.

Simply stated, a wind turbine works the opposite of a fan. Instead of using electricity to make wind, a turbine uses wind to make electricity.

The wind turns the blades, which spin a shaft, which connects to a generator and makes electricity The electricity is sent through transmission and distribution lines to a substation, then on to homes, business and schools.

Wind energy offers many advantages over conventional power production, including minimal environmental impact, reduced dependence on fossil fuels, and potential long-term income for property owners who lease land for wind farms.

If you're thinking about installing a wind turbine to power your Iowa farm, school or business, there are many details to consider.

The following printable fact sheets provide answers to common questions and a checklist to walk you through some of the basic steps you'll need to make a sound, reasoned decision:

WindConnect - Tapping into Wind Energy Q&A [PDF]

WindConnect - Custom Wind Systems Checklist [PDF]

Photovoltaics

Photovoltaic cells collect solar energy and convert it directly to electricity. This technology uses semiconductor material to convert sunlight directly into electricity - if you have a solar calculator or watch, you're already using photovoltaics.

The advantages of a photovoltaic (PV) system are numerous: it's non-polluting, there are no moving parts, it operates silently and requires little maintenance. Photovoltaic power can also be stored in deep-cycle batteries for evening or back-up use.

A PV system produces low-wattage direct current electricity, compared to the 120-volt alternating current supplied by utility companies. This means PV set-ups require different wiring, along with an inverter to be able to run equipment.