Using the power of gravity and water to produce energy has several benefits. Conventional hydroelectric generation is a relatively low-emissions form of renewable generation. It does not require the combustion, or use, of fuel to provide electricity — although the Ludington station does use electricity from the grid, which includes fossil- and nuclear-fueled generation, to pump water into the reservoir. Hydroelectric generation has the additional benefit of being dispatchable — it can be turned on or off quickly in response to system demand. This makes hydroelectric more like baseload generation options such as coal, and combined-cycle natural gas[*], and separates it from other renewable options like wind and solar, which are non-dispatchable.
Some challenges associated with hydroelectric generation are that it typically requires a dam that blocks river flows, which can impede fish passage. The dams and the reservoirs they create cause substantial changes in riparian ecosystems and can displace a mix of human and wildlife populations. Additionally, although hydroelectric is a renewable energy resource, the creation of large reservoirs can cause the release of substantial amounts of methane gas. This methane is generated by bacteria that digest and decompose organic waste, algae, and vegetation present in the often cold, oxygen-depleted reservoir water. This process can be compounded by nitrogen-rich runoff from agricultural fields, which encourages algal growth in the reservoirs.
[*]Traditional nuclear technologies are considered less dispatchable as they are designed to run at, or very near, full capacity, with very little variation. However, Gen. 4 reactor designs are expected to allow more flexible operations.