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YOUR RENEWABLE ENERGY OPTIONS
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Hydropower
Currently, hydropower accounts for 10% of our nation’s energy supply and about 96% of our renewable energy production1. In Massachusetts, about 1% of our energy comes from hydropower facilities2. Hydropower uses the kinetic energy of falling water to power the blades of a turbine, which in turn produces electrical energy. Using the natural force of our rivers to create non-polluting power provides many unique benefits, but can also present serious environmental concerns. Characteristics such as size and ecosystem impacts should be carefully considered when evaluating the merits of every hydro project. Hydropower facilities can be one of three main types: impoundment, diversion or pumped storage.
Impoundment
An impoundment facility uses a dam to store water, which can then be released to generate electricity when needed. The facility below is located on Quinebaug River in Massachusetts.
Diversion
A diversion facility channels water through a passageway which may or may not require a dam.
Pumped Storage
Pumped storage takes water from a lower reservoir and pumps it into an upper reservoir during off-peak production time. The water is then released from the upper reservoir to generate electricity during peak demand hours.
The picture below is of PG&E's Bear Swamp pumped storage facility in Rowe, MA. The facility generates over 600 MW of electricity.
Benefits of Hydropower
While large scale hydropower can cause major ecological damage to river ecosystems, smaller plants provide a cost effective, and generally emissions free alternative to polluting fossil fuels. Since hydropower does not rely on any fuel for operation, it is not subject to the periodic price spikes common to other generating sources (such as oil and gas). Hydropower facilities are generally very efficient and require little maintenance. This combined with the long life of the facilities, some of which have been operating for several decades, makes hydropower a low cost alternative to traditional power production. The electricity produced by hydropower is generated from a reliable and predictable resource and can be be brought on line quickly to generate electricity during peak demand times.
On the other hand, prime sources for hydroelectric sites are limited, and because any given river has a maximum flow potential, there are not always options for expansion. Upgrading equipment can increase the efficiency and therefore the output of existing systems, but many factors must be evaluated to determine if this option is economically feasible, one of which is the environmental considerations.
Environmental Issues
The installation of hydro facilities along river fronts has been shown to disrupt a river’s ecosystem in many ways. Whether water is diverted from a stream, or blocked behind a dam, the natural flow of the water is disturbed, thereby changing water levels, withholding important nutrients from flowing downstream and often causing a rise in water temperature. River systems require a balance of nutrients and sediment to maintain fish, wildlife and plant habitats. An excess amount of sediment being released from a hydro facility can bury river bottoms, important breeding grounds for many species, including numerous fish. Conversely, dam structures block sediments, which can create a deficiency of nutrients for downstream habitats and a dangerous build-up of pollutants for their upstream counterparts. Eventually the sediments that build up behind a dam must be removed, often at great expense and risk to downstream habitats. Dramatic changes in water levels, which are created by the sudden release of water, can also disrupt wildlife/plant habitats by altering natural cycles of growth and reproduction.
One of the most public issues regarding hydropower facilities is the issue of interference with fish habitats. The presence of dams inhibits fish from moving freely up and downstream, which can result in the disruption of feeding and reproduction cycles. Also, some equipment used at hydropower facilities, such as turbines, kill the fish that pass through the system. In some locations, alternative methods have been developed to help alleviate this problem. ‘Trucking’ fish from downstream to upstream areas and the installation of fish ladders, such as the one below, are two such methods. However, transporting fish in these ways can disorient them and make them more vulnerable to predators.
Evaluating Hydropower as a Resource
Comparing the pros and cons of hydropower can be a difficult task and should be performed on a case by case basis. There are approximately 75,000 large dams and tens of thousands of smaller dams throughout the USA, some of which are no longer being used, are poorly maintained or are too old to funtion in a safe and efficient manner. Prolonging the life of an otherwise outdated facility inhibits natural ecosystems from being restored. However, breaching dams that have been found to severely damage the river ecosystem is a serious and expensive alternative. Still, in some cases dam breaching is the best option for the river. Suitable sites with dams already in place should operate to their fullest potential while they are still economically and environmentally viable. Advancements in turbine technology and upgrading the efficiency of existing equipment can help facilities maintain both these objectives. One of the most promising aspects of hydropower generation is the use of small scale systems.
Small Scale Hydropower
Small scale hydropower is usually defined as a facility with 30 megawatts or less of generating capacity. Small scale projects are generally considered to have a lower impact on the environment than their larger counterparts. However, hydropower facilities as small as 5 MW have been shown to have adverse effects on the environment. To determine if a facility is truly low impact it must be evaluated on a number of different levels regardless of its size. Institutions such as the Low Impact Hydro Institute, whose link is listed below, have been established to provide this service.
For more information on Hydro Power:
The Low Impact Hydro Institute
American Rivers
The Massachusetts River Restore Program
The Federal Energy Regulatory Commission
(The federal agency responsible for licensing hydro facilities)
1.http://www.eren.doe.gov/state_energy/policy_casestudies_massachusetts.cfm 2.http://www.americanrivers.org/
