Renewable Energy

Enlightened Pragmatism - the environment and the economy are not mutually exclusive In today's business climate, an energy strategy that includes renewable sources must serve the dual bottom line of being environmentally responsible and economically practical. Thanks to technology advances and a growing corporate interest in green power, it can.

Emergence of Green Power Electric power generated from renewable sources of energy is generally referred to as "Green Power." These renewable sources include solar (sun radiation), wind (movement of air), hydro (movement of water), geothermal (heat from the earth), biomass (plant-based and waste fuel, including the gaseous form, biogas), and hydrogen (derived from renewable and fossil sources) Northern focuses primarily on solar, wind, biogas, and hydrogen in our renewable energy solutions because they are currently the most commercially viable for our customers.

Over the past twenty years, a number of market drivers have converged to make green power a viable option for companies who want to minimize the impact of their processes while meeting their economic objectives.

Renewable Sources

Solar Solar energy is derived from the sun's rays. Photovoltaic cells are arranged in arrays that collect the solar energy and convert it to direct current (DC). That DC current is then used as is or is inverted to alternating current (AC).

Traditionally, solar power systems were used for remote applications that were not connected to the grid, but in recent years, they have been gaining growing acceptance in grid-connected applications where customers are seeking supplemental power. For example, the power output of a solar power generation system generally matches the standard peak load demand for air conditioning, which makes it ideal for peak shaving applications where a customer is looking to reduce peak demand charges.

Benefits of Solar Power:

• Environmentally benign and universally available

• Modular and scaleable, incrementally from a few watts to hundreds of watts

• No fuel costs and delivery

• Minimal maintenance

• Proven commercial technology

Wind Wind energy is converted into electricity as air currents propelling a rotor which in turn spins a generator to produce variable frequency AC power. The variable frequency AC power is rectified into DC, conditioned and inverted back to constant frequency AC power for distribution and/or transmission. Wind power was originally used to power radios in areas without electricity in the mid-1900s but was quickly adapted to off-grid remote applications in the 1970s. Wind turbines for these applications are generally rated below 10 kW because the off-grid loads are small.

Utility-grade wind turbines are typically rated from 50kW to 2.5MW and above. Wind turbines, mostly augmenting diesel-powered generation, have provided utility power to isolated community or village power applications in high wind areas since the 1980s. On-site power systems for municipal, industrial or commercial applications using wind turbines require access to average wind annual speeds of 11-12 mph.

Wind turbines, when grouped together into a small power plant are called wind farms. The bulk electricity generated by a wind farm can be fed back to the grid to be distributed or transmitted to end-users. Traditional land-based wind farms are very common in Europe and are becoming more accepted in the North America. Offshore wind farm projects are now emerging in Europe and are being considered in the U.S. because they allow higher generating capacities and avoid the cost and siting issues land-based projects sometimes present. Larger wind turbines found in utility wind farms require annual average wind speeds above 12 mph to be cost competitive.

Benefits of Wind Power:

• Limited environmental impact: mostly visual

• Competitive market pricing

• No fuel costs and delivery

• Proven commercial technology

Biogas When we generate electricity on-site with biogas, the benefits to the environment are twofold. First, we mitigate very damaging greenhouse gas emissions and second, we avoid the inefficiencies of transmission from centralized generating facilities.

Biogas is a byproduct of the breakdown of organic material. It can be derived from waste treatment processes such as solid material landfills and digesters in wastewater treatment facilities. It is a combination of methane and carbon dioxide. The methane content is over twenty times more powerful a greenhouse gas affecting the atmosphere than the carbon dioxide. Therefore, it is crucial to mitigate the effect of the biogas by removing the methane. This is commonly accomplished through flaring the gas.

Alternatively, if biogas is burned as a fuel to generate electricity, we harness the energy with no net change to the carbon inventory in the atmosphere. Biogas is a biotic source (as opposed to a fossil-based source) of natural gas. When biogas is burned as a fuel or flared to remove the methane, it only releases the carbon dioxide that the original organic material would have released naturally as it decomposed. In contrast, when fossil-based natural gas is burned as a fuel, it adds to the atmospheric carbon inventory by removing carbon from the lithosphere (solid part of the earth) and introducing it into the atmosphere as carbon dioxide, a byproduct of burning the fuel.

Net Air Emissions (lbs/MWh)
Resource	CO2	NOx	SO2
Landfill Gas	0.0	< 2.9	0.1
Coal	2,248.9	5.9	13.2
Oil	1,672.1	4.2	11.7
Natural Gas	1,118.9	1.7	0.1

Landfill Gas Solid waste is brought to landfills and buried under a layer of soil, usually clay, called a cap. This creates an anaerobic (oxygen-free) environment that produces significant amounts of methane gas. This gas is considered low energy-content gas, as it is comprised of 57 percent methane, 42% carbon dioxide, and less than 1% each of nitrogen, hydrogen, and oxygen. The gas can also contain trace quantities of other compounds depending on the contents of the landfill.

The gas can be collected with a gas collection system, which is a series of drilled wells and connecting pipes that bring the gas to a central place. Water, used in the process of collecting the gas, must be removed by dehumidifying the gas. The gas can then be used directly in reciprocating engines or burned in furnaces. If it is further processed to remove the carbon dioxide from the gas, then compressed and filtered, the gas is then suitable to fuel gas turbines and fuel cells.

Large landfill operations generally produce enough gas to generate anywhere from 2MW to 15MW of electricity. The electricity can be generated on-site at the landfill, or the gas can be transported off-site to nearby manufacturing or commercial facilities where it can be used to co-generate electricity and heat in a CHP On-site Power system. The heat and electricity can be used to replace or offset the power ordinarily supplied by the utility.

Digester Gas Wastewater treatment facilities use a process of anaerobic digestion to breakdown solids in the treatment of organic waste such as plant or animal matter from municipal sewage, livestock manure, and food processing waste. This biological process produces digester gas, which is comprised principally of methane and carbon dioxide. Commercially available digesters can produce gas containing from 55% to 75% pure methane. Depending on the source of the waste and the system design, it is possible to produce gas with even higher percentages of methane.

The amount of biogas that can be produced in an anaerobic digester is typically enough to use on-site to offset energy demand of the waste treatment facility, livestock or dairy operation, or the food processing operation that produces the waste. The capacity is in the range of 25-200 kW, which makes the application suitable for reciprocating engines, microturbines and fuel cells.

Benefits of Biogas:

• Byproduct of a natural process

• Modular and scaleable

• Avoids greenhouse gas emissions