Thanks for the additional information which I hope my readers access.
]]>This is a great way to produce power in remote mountains. Unfortunately there are few remaining stream sites that are suitable. Francis turbine systems can run for decades with little or no maintenance. Ordinarily, no major dam impoundment is employed; so capital costs per unit of capacity tend to be low.
Hydropower production is a function both of penstock head pressure and water mass flow. The head pressure is generally fixed by the physical installation, the higher the better, because less water volume is needed to produce each unit of power, but in most cases available water volume varies greatly with the season. Since no significant impoundment is available, power production is limited to real time stream flow rates. So while stream flow rates can sometimes reach the turbine generators’ nameplate capacity, often the stream flow rate, which is obviously dependent on seasonal precipitation, won’t sustain even 10% of installed nameplate capacity. (This is similar to wind turbines where nameplate capacity is related to 27 MPH wind speed. Wind turbines rarely operate in sustained wind speeds in excess of 18 MPH.) So it sort of turns out that capital is stranded in the turbine generators that are sized large enough to capture all the maximum stream flow, but are 90% larger than needed for minimum flow rates. Still it’s probably the best way to electrify remote mountain villages that have year-round stream flows. The ideal situation is to connect the small hydropower plant to a major utility grid. Then when stream flow is at maximum, nearly full nameplate capacity can flow into the grid, which generates revenue for the hydroplant operators. When stream flow is minimum the operators can consume all their power locally, or even draw off the grid.
Such an ideal installation exists in the US on Deep Creek near North Port, WA. See:
The private owner operator collects about $90,000 each year from the local power grid. The owner has 400 KW of nameplate capacity installed, but only a few months of the year produce enough stream flow rate to keep both his turbines spinning. Notice the scenic waterfall in the linked pictures. That’s electrical power and potential revenue from the local power grid going to waste down the creek. Gordon owns three 100 KW turbines (shown sitting on the powerhouse deck in the linked pictures), which could capture more of the maximum stream flow. But he hasn’t bothered to install the extra turbines, because with climate change affecting precipitation patterns it’s a gamble whether enough stream flow will be available to ever justify the installation costs.
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