Process
We are generating power on a run of river (RoR) dam--which is a very benign way to produce power. Our site is located at an existing dam built in the 18oo's and there are dams upstream and downstream from us. The Burnshire dam is 13 feet tall and is used only to create head (water elevation). All water either passes over the dam or is routed through the turbines so as is typical of RoR projects, there is no substantial impoundment (reservoir) or large area of flooded land. Before passing through the turbines the water is screened for debris. We pull countless plastic bottles, flip flop shoes (though never a pair), and other various trash out off of the racks and dispose of the trash properly. The water then goes through the turbines, out through the tail race and back into the river immediately below the dam. Run of river hydropower does not alter stream flow--the water either flows over the dam (wasted energy) or through the turbines (green energy)-- regardless, river flow remains the same.
In our case, we do not use a penstock but instead a very small forebay so the water path is equivocal no matter which route it follows. Diagram adapted from: http://www.goodenergy.cl/eng_hydropower.html
What makes us different?
The prime mover at our site is falling water. The kinetic energy of the water falling causes the runner inside the turbine to spin producing mechanical energy which is then converted to electrical energy inside the generator. In general, hydropower converts mechanical to electrical energy with an efficiency of up to 93% (compared to a steam turbine like coal or NG electric production -- which is 60%).
We are using a permanent magnet generator (PMG) coupled to and controlled by a regenerative inverter. Our generator operates very efficiently under varying water flow conditions so we can match power production to the water flowing in the river. A PM generator produces variable frequency and voltage proportional to the rotational speed of the turbine. However this "variable speed electricity" is unusable so it is then transformed inside the inverter from A/C to DC power and then back to grid matched A/C power. Transforming energy always creates a net loss, usually as waste heat (the first law of thermodynamics) but offsetting this, the PM generator operates efficiently over a range of speed so the total electrical energy produced long term is higher (and with added environmental and operational benefits).
Where else does this technology exist? Ever see a Prius or ride in an elevator? Both recapture energy in a similar way. In 2013, 17% of all wind turbines used PM generators and nearly all new non hydraulic commercial elevator installations use PM motors with regenerative inverters (so when you ride the elevator down, you are making green energy!). Conveyor belts, cranes, pump jacks, and other reciprocating, high inertia processes use regeneration as well. As far as we know, we are the third developed and fourth interconnected PMG hydropower installation in the country.
Distributed power generation, like ours, is produced where it is needed, at the user level. There are no line losses caused by transporting power from distant coal plants, substation losses, multiple transformer step up/down losses, or other conversion losses. There is also security benefit from having distributed generation and not being completely reliant on a single, central source of power.
Adapted from: http://www.mpoweruk.com/energy_efficiency.htm
The above example shows generation, distribution and end user energy losses typified by a very inefficient incandescent lamp. 65% losses at generation are typical of fossil fuel plants (hydropower has a conversion loss of about 7-10%). Transmission losses from a distant power plant to the end user are approximately 6%. Said another way, more than 65% of the waste products (CO2, coal ash, SO2, heavy metals, etc..) at a typical fossil fuel power plant are created for power that never reaches the end user.
Future
Our process and the equipment have a lot to teach us and the world. Incredible advances in power electronics have occurred in the last ten years but again, few people have tried to translate these advances onto the hydropower industry. We will. For example, we are optimizing river flow matching logic to capture the most energy from the river that is possible but without altering flow. As well, we are developing ladder logic and controls that will completely automate the plant and reduce the controls necessary at typical generation sites --our logic controller could fit in a shoe box-- and banks of electrical cabinets and heavy switch gear have been eliminated (our generator is the size of a college dorm refrigerator and weighs 1/3 less than a typical generator).
Future studies will likely include evaluation of scalability to determine the range of operation of the modern generation equipment, efficiency trials for overall production, DC bus integration of other renewable, with the intent to develop turn key controls cabinets and logic processes built by hydro operators for hydro operators. This is how our company will grow and we can leverage our knowledge to help others reduce emissions and produce green power. It's a win/win/win/win for us, our future customers, the planet, and most importantly, our children.