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Power - Hydro turbine - Residential - 4.0 kW - Off-grid / Canada
Case study assignment
You are a homeowner investigating different options for providing electric power to your off-grid home, located in the southern interior of British Columbia, Canada. Grid power is not available in the area, due to its remoteness. Most people in the area use diesel engines to power electric generators ("gensets"). A genset operates inefficiently when lightly loaded, so the gensets charge batteries, with AC loads powered through an inverter.
You have calculated your electricity requirements and determined that they average around 5 kWh per day; you have the option of heating with firewood and using propane for cooking. Your peak load, ignoring momentary spikes for the starting of motors, is around 3 kW.
You would like to compare a genset/battery/inverter system to a micro hydro system. Losses in the battery and inverter would total about 25% of the output of the genset. The micro hydro project would make use of the flow in an existing water line that transports water from a nearby creek to an irrigation system. A local supplier is proposing a turgo turbine from Energy Systems and Design. This turbine normally supplies up to 1.5 kW for battery charging. But other off-grid users have had good experiences using this robust turbine to produce 3 to 4 kW, employing 2 or 3 jets and flow rates up to 0.028 m³/s. In such systems dump loads and a controller supplant the battery.
Site information
Your home is located in a rugged, near-desert district west of Lillooet (BC), Canada. A stream with flow exceeding 0.034 m3/s (1.6 ft3/s) throughout the year passes nearby. In 1970, a 12.7 cm diameter PVC water line was installed to connect an agricultural irrigation system to the creek. Between the creek and the point where you would site your powerhouse, this 300 m water line falls around 35 m vertically. The irrigation system supplies approximately 0.009 m3/s (150 gpm) of water to 12 hectares of crops. The waterline is buried below the frost line. You contacted an equipment supplier who provided you with a chart (below) showing hydraulic losses in 12.7 cm diameter PVC pipe as a function of flow rate. The proposed site for the powerhouse is about 100 m from your home.
Financial information
The installed cost of a 5 to 7 kW diesel genset is around $7,500. Deep-cycle batteries would cost around $2,000 and an inverter an additional $2,000. The purchase of the micro hydro turbine, an alternator, and a Thompson and Howe load controller would total around $7,500.
You are fairly handy and are willing to work on the system yourself, both for installation and for operation and maintenance, but would like to have a micro hydro consultant visit your site and ensure that your proposed system makes sense. You will procure necessary permits yourself.
The delivered cost of diesel fuel is around $0.70/litre. You expect this to rise at a rate slightly higher than general inflation. When operated at its nominal capacity, the genset consumes about 0.5 litres of fuel per kWh of output.
You would borrow around half the money required for this project, with a 15-year mortgage at 8%.
You expect to be living in your home for the rest of your life, or approximately 35 years. You are interested in comparing not just the financial viability of micro hydro versus diesel genset, but also the reductions in greenhouse gases over this period.
Prepare a RETScreen study, documenting any assumptions that you are required to make, and report on the significant conclusions from this analysis.
Case study assignment
You are a homeowner investigating different options for providing electric power to your off-grid home, located in the southern interior of British Columbia, Canada. Grid power is not available in the area, due to its remoteness. Most people in the area use diesel engines to power electric generators ("gensets"). A genset operates inefficiently when lightly loaded, so the gensets charge batteries, with AC loads powered through an inverter.
You have calculated your electricity requirements and determined that they average around 5 kWh per day; you have the option of heating with firewood and using propane for cooking. Your peak load, ignoring momentary spikes for the starting of motors, is around 3 kW.
You would like to compare a genset/battery/inverter system to a micro hydro system. Losses in the battery and inverter would total about 25% of the output of the genset. The micro hydro project would make use of the flow in an existing water line that transports water from a nearby creek to an irrigation system. A local supplier is proposing a turgo turbine from Energy Systems and Design. This turbine normally supplies up to 1.5 kW for battery charging. But other off-grid users have had good experiences using this robust turbine to produce 3 to 4 kW, employing 2 or 3 jets and flow rates up to 0.028 m³/s. In such systems dump loads and a controller supplant the battery.
Site information
Your home is located in a rugged, near-desert district west of Lillooet (BC), Canada. A stream with flow exceeding 0.034 m3/s (1.6 ft3/s) throughout the year passes nearby. In 1970, a 12.7 cm diameter PVC water line was installed to connect an agricultural irrigation system to the creek. Between the creek and the point where you would site your powerhouse, this 300 m water line falls around 35 m vertically. The irrigation system supplies approximately 0.009 m3/s (150 gpm) of water to 12 hectares of crops. The waterline is buried below the frost line. You contacted an equipment supplier who provided you with a chart (below) showing hydraulic losses in 12.7 cm diameter PVC pipe as a function of flow rate. The proposed site for the powerhouse is about 100 m from your home.
Financial information
The installed cost of a 5 to 7 kW diesel genset is around $7,500. Deep-cycle batteries would cost around $2,000 and an inverter an additional $2,000. The purchase of the micro hydro turbine, an alternator, and a Thompson and Howe load controller would total around $7,500.
You are fairly handy and are willing to work on the system yourself, both for installation and for operation and maintenance, but would like to have a micro hydro consultant visit your site and ensure that your proposed system makes sense. You will procure necessary permits yourself.
The delivered cost of diesel fuel is around $0.70/litre. You expect this to rise at a rate slightly higher than general inflation. When operated at its nominal capacity, the genset consumes about 0.5 litres of fuel per kWh of output.
You would borrow around half the money required for this project, with a 15-year mortgage at 8%.
You expect to be living in your home for the rest of your life, or approximately 35 years. You are interested in comparing not just the financial viability of micro hydro versus diesel genset, but also the reductions in greenhouse gases over this period.
Prepare a RETScreen study, documenting any assumptions that you are required to make, and report on the significant conclusions from this analysis.
Solution
The worked-out solution is the data file selected from within the RETScreen Project Database. The user automatically downloads the Project Database file while downloading the RETScreen software.
Teacher's notes
Results
A micro hydro system was built for an off-grid family ranch in a remote area west of Lillooet, B.C. over a period of time in the 1990's. It was put together with local talent and quite a bit of volunteer labour from all concerned. It replaced an existing homemade micro hydro system, taking advantage of an existing gravity water system, with a more efficient and reliable system offering more power. This new system provided electrical service, and also furnished domestic hot water and a significant amount of space heating.
System description
The system is based on a Canadian turbine, the Energy Systems and Design Turgo with 10 cm runner, well tested in battery charging applications where it generates up to 1.5 kW. It is perfectly capable of generating more than 3 kW, as it does in this three-jet system. It drives a 12 kW brushless AC alternator. Although larger than strictly necessary, the alternator proved to be reasonably efficient and the extra mass comes in handy acting as flywheel to help in motor starting.
Lessons learned
Micro hydro technology can be by far the most cost effective solution to the problem of providing basic electrical service to an off-grid residence, even when the system output seems very small indeed. Europeans and many off-grid consumers can testify that the first one hundred kWh per month makes possible the majority of benefits associated with electric service, and that a couple of hundred kWh per month permits a higher standard of living. These same consumers often report that a 2.5 kW inverter adequately meets their household power requirements.
Although the homeowner could have invested more money, effort and engineering to generate more power from the available water resource, a 3.2 kW system was most satisfactory. Despite the high heating requirements of the log home, excess power was being dumped for much of the year. Lack of opportunities for getting an economic return for excess power often limits the size of projects that can be justified. An opportunity to create value from surplus power would be welcomed by many micro hydro users.
Photos
The Residential Off-Grid Micro Hydro System Shared an Existing Gravity Water Pipe with an Irrigation System, British Columbia, Canada
Adding a Third Jet Raised the System Output from 2.5 to 3.2 kW, British Columbia, Canada
References
The worked-out solution is the data file selected from within the RETScreen Project Database. The user automatically downloads the Project Database file while downloading the RETScreen software.
Teacher's notes
- The maximum hydraulic losses are calculated using the total flow rate, the length of the PVC pipe between the intake and the powerhouse, and the chart supplied in the assignment. The total flow rate (turbine plus irrigation) is around 0.037 m³/s. From the chart, this results in around 5 m of head losses per 100 m of pipe. For 300 m of pipe, this is 15 m of head lost, out of a total of 35 m, or 43%. Note that the total flow rate is slightly higher than the lowest flow in the stream, so for a brief period of the year, either the irrigation rate or the turbine output may be slightly reduced, unless the water exiting the powerhouse can contribute to irrigation. This situation will be very rare, however, and is ignored here.
- The generator efficiency of 88% is lower than is characteristic of the generators in larger hydro projects, but is appropriate for a 2 to 10 kW alternator.
- The flow duration curve for the creek is unknown, except for the minimum flow rate-0.034 m3/s. Because this flow rate exceeds the water requirement (with the exception noted above), it has been entered for all cells in the flow duration curve since higher flow rates are irrelevant (only "0.03" is displayed in the worksheet).
- The 3.6 kW capacity of our system is sufficient to meet our peak load, but at most points in time the home will require far less power, with the excess dissipated as heat in the dump load. The 5 kWh per day average load is equivalent to a constant load of around 208 W. This has been entered for all cells in the load-duration curve.
- The feasibility study costs reflect the assistance provided by an outside consultant.
- Small diesel gensets are relatively inefficient. In the greenhouse gas analysis, their efficiency at nominal loading (the point at which they will generally operate when charging batteries) is estimated at 15%.
- Other off-grid power systems, such as those based on photovoltaics or wind turbines, would be unable to match the low cost of small hydro at this site, although they might also be more attractive than the diesel/battery system.
Results
A micro hydro system was built for an off-grid family ranch in a remote area west of Lillooet, B.C. over a period of time in the 1990's. It was put together with local talent and quite a bit of volunteer labour from all concerned. It replaced an existing homemade micro hydro system, taking advantage of an existing gravity water system, with a more efficient and reliable system offering more power. This new system provided electrical service, and also furnished domestic hot water and a significant amount of space heating.
System description
The system is based on a Canadian turbine, the Energy Systems and Design Turgo with 10 cm runner, well tested in battery charging applications where it generates up to 1.5 kW. It is perfectly capable of generating more than 3 kW, as it does in this three-jet system. It drives a 12 kW brushless AC alternator. Although larger than strictly necessary, the alternator proved to be reasonably efficient and the extra mass comes in handy acting as flywheel to help in motor starting.
Lessons learned
- Every site is unique.
- The supply of renewable energy from the micro hydro system greatly exceeds the home's demand.
- This system performed slightly better, in terms of satisfying sensitive and transient loads, than a battery/inverter system rated at 2.5 kW, and also provided lots of heat.
- This direct AC system does not require a careful assessment of the demand, as might a micro hydro battery charging system, and is simpler and more reliable than systems incorporating batteries.
- Maintenance requirements on this system are minimal. Bearings need to be replaced every 7 years. The intake needs to be cleaned, a fifteen-minute task, monthly or, during fall, even weekly.
Micro hydro technology can be by far the most cost effective solution to the problem of providing basic electrical service to an off-grid residence, even when the system output seems very small indeed. Europeans and many off-grid consumers can testify that the first one hundred kWh per month makes possible the majority of benefits associated with electric service, and that a couple of hundred kWh per month permits a higher standard of living. These same consumers often report that a 2.5 kW inverter adequately meets their household power requirements.
Although the homeowner could have invested more money, effort and engineering to generate more power from the available water resource, a 3.2 kW system was most satisfactory. Despite the high heating requirements of the log home, excess power was being dumped for much of the year. Lack of opportunities for getting an economic return for excess power often limits the size of projects that can be justified. An opportunity to create value from surplus power would be welcomed by many micro hydro users.
Photos
The Residential Off-Grid Micro Hydro System Shared an Existing Gravity Water Pipe with an Irrigation System, British Columbia, Canada
Adding a Third Jet Raised the System Output from 2.5 to 3.2 kW, British Columbia, Canada
References
- Davis, S., Microhydro: Clean Power from Water, 2003.
- Maxwell, S., "Homestead Hydropower: Harness the power of flowing water for clean, sustainable home electricity," Mother Earth News Issue # 208, February/March 2005.
