# Turbine Efficiency with Generator load

• dilipbhanu
In summary, the conversation discusses the development of a 2KW hydro turbine prototype with a brushless DC permanent magnet generator connected. The generator has been tested and shows a maximum output of 2001 Watts at 1930 RPM. The efficiency of the system is being questioned, with the input power being calculated based on hydrostatic head and the output power being measured with the generator connected. However, without a load or additional testing, the efficiency cannot be accurately determined. The conversation also mentions the use of a centrifugal pump to create hydrostatic head and the challenges of calculating turbine efficiency without a generator.
dilipbhanu
Hi, I have developed a 2KW hydro turbine prototype with a generator connected.

Generator Type - Brushless DC Permanent Magnet (16Pol-18Slot) (2000Watts, 2000 RPM, 54VDC)

Generator test report (by manufacturer) is given below;
Code:
RPM                Volts             Current
1000               29.8                34.7
1500               44.65              35.2
1900               56.5                35.3
1930               57.5                34.8
2000               59.5                36.2

With the Generator connected to Turbine, I am able to achieve 1930 RPM with no Load connected. Since the generator test report shows 57.5 Volts * 34.8 Amp = 2001 Watts at 1930 RPM, Can i assume the same to be my system output efficiency ? or I will have to add dummy load to generator to find final system efficiency.

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You will certainly have to perform tests .Turbine rpm will drop considerably when generator is loaded .

Do you have a performance characteristic plot for this turbine ? How did you arrive at the 2KW output figure ?

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A centrifugal pump is used to create hydrostatic head.

Gauge Pressure: 2.5 kg/cm2 = 25 Meter of Water column
Flow = 8lps
Input Watts = Mass*Gravity*Head = 25*9.81*8 = 1962 Watts

dilipbhanu said:
With the Generator connected to Turbine, I am able to achieve 1930 RPM with no Load connected. Since the generator test report shows 57.5 Volts * 34.8 Amp = 2001 Watts at 1930 RPM, Can i assume the same to be my system output efficiency ? or I will have to add dummy load to generator to find final system efficiency.
Taking a step back here, you aren't comparing two different powers to each other (that I can see), so it isn't even clear what calculation you are doing to get efficiency. The only two powers implied there are "no load" (zero) and loaded at 2001 Watts. Since the power output at no load is zero, your effficiency must also be zero. Since your power output loaded is known, but your power input isn't known, your efficiency can't be calculated.

So, what exactly are you calculating? Are you really just asking if loaded and unloaded rpm are the same? Then no (as indicated).
A centrifugal pump is used to create hydrostatic head.
Please tell me you aren't trying to create a perpetual motion machine? Whatever you are doing, since your input and output numbers are roughly the same, and since the output doesn't include inefficiency, your 2000W (output) pump can't possibly power your 2000W (output)generator at full load.

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I am using a 5HP (3728.5 Watts) pump to create hydrostatic head. Pump efficiency is 52.6% at duty head of 25 Meters with flow rate of 8LPS

Hence, ignoring pump losses, I have taken Water Horse Power (WHP) 1962 Watts as input energy and trying to convert this energy to mechanical energy at turbine shaft.

Turbine diameter is 8 inches and it rotates at constant speed of 2080 RPM with bare shaft (without generator connected)
When the said generator is connected to Turbine, its RPM comes down to 1930 (compared to bare shaft RPM)

Generator is rated for 2150 Watts at 2000 RPM, hence required generate torque is 10.266 N.m
Torque required to prevent the turbine from rotating = 17.5 N.m (based on water mass discharged, velocity and turbine radius)

Is there a way to calculate turbine efficiency without a generator ?

dilipbhanu said:
Is there a way to calculate turbine efficiency without a generator ?
Not with the information provided. You will either need to provide a load (doesn't have to be electrical as long as you can measure the torque and rpm) or do a computational fluid dynamic modeling of the turbine. Every turbine performs differently and the rpm when unloaded just isn't a useful piece of information.

## 1. What is turbine efficiency and how is it calculated?

Turbine efficiency is a measure of how well a turbine converts the energy from a fluid (such as steam or water) into mechanical energy. It is calculated by dividing the actual power output by the theoretical power output, and is expressed as a percentage.

## 2. How does the generator load affect turbine efficiency?

The generator load, or the amount of power being drawn from the generator, can significantly impact the efficiency of a turbine. As the load increases, the turbine must work harder to generate the required amount of power, leading to a decrease in efficiency.

## 3. Can turbine efficiency be improved with different generator loads?

Yes, the efficiency of a turbine can be improved by adjusting the generator load. Generally, operating a turbine at a lower load can result in a higher efficiency, as the turbine is not working as hard and experiencing less friction and resistance.

## 4. How does the design of a turbine affect its efficiency with different generator loads?

The design of a turbine can greatly impact its efficiency with different generator loads. Factors such as the size and shape of the blades, the number of stages, and the type of fluid being used can all affect the efficiency of a turbine at various loads.

## 5. Is there an optimal generator load for maximum turbine efficiency?

The optimal generator load for maximum turbine efficiency will depend on the specific design and operating conditions of the turbine. In general, however, operating at a load that is neither too high nor too low can result in the highest efficiency for a turbine.

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