Hydro Power

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Hydro Power
(This page was kindly donated by jatsgreenpower.com)

Small Hydro Power Systems

The following information is provided to help you consider small to mid-sized hydroelectric generators that are designed to be 12, 24, or 48 volt battery chargers. A stream or creek is needed - they operate with a relatively small volume of water. They charge batteries 24 hours per day, and the power can be drawn from the battery. As little as 100 gallons per minute (GPM) falling only 10 feet through a pipe, or 5 gallons per minute falling 200 feet through a pipe can supply enough power to run a small household.

A small hydroelectric system can also work well with solar modules, both charging the same batteries. Whenever rainy, the solar modules are putting out less power, but the hydroelectric system will likely be producing at its peak.

A typical AC power hydroelectric system designed to deliver on-demand 120/240 VAC power is not practical for most people because you need a constant water supply large enough to supply the peak power output that will be required, usually a minimum of several thousand watts requiring hundreds or even thousands of gallons per minute, depending upon the pressure available. Besides requiring large amounts of water, these turbines require large pipe diameters and expensive regulating systems to maintain proper frequency and voltage at all times.

For most small to mid-sized alternative energy systems even smaller DC units can provide you with a full range of power. For example, a 500 - 1000 watt unit is sufficient to supply enough energy for a variety of applications, whether to act as a primary charge source or be used in a hybrid system.

How much power can it generate?

The amount of power available depends on the dynamic head, the amount of water flow and the efficiency of the turbine/generator combination. To get an idea about available power in watts, multiply the head in feet, times flow in GPM, times 0.18 times efficiency. Turbine efficiency ranges from 25% to 50%, with higher efficiency at higher heads. To get a rough idea, use 0.30 (representing 30%) as a multiplier for efficiency.

Pipelines and Pressure

A hydroelectric turbine operates from the pressure at the bottom end of a pipeline. This pressure, usually measured in pounds per square inch (PSI) is directly related to the head, or vertical distance from where the water goes into the pipe at the top of the pipeline, to the turbine located at the bottom of the pipeline. The pressure at the lowest point of a pipeline is equal to 0.433 times the vertical distance in feet, called head. Pressure is important because it is a determining factor in how much power is available and in what type of pipe is required. Polyethylene pipe can be used for pressures up to 100 PSI, PVC pipe is available with pressure ratings from 160 to 350 PSI and steel pipe can withstand 1000 PSI or more. Check with you local plumbing supplier for pipe ratings.

Pipe diameter is very important. All pipelines will cause the water flowing in them to lose some energy to friction. The pipe must be large enough for the maximum quantity of water it will carry. The pressure at the bottom of a pipeline when water is not flowing is called static pressure. When water is flowing through the outlet or nozzle of the hydroelectric turbine, the pressure at the outlet is the dynamic pressure or running head.

If you install a gate valve on the pipeline just above the turbine and a pressure gauge on a "T" fitting just above the gate valve, you will read the static pressure on the gauge when the valve is closed and the dynamic pressure when the valve is opened. The maximum power that can be delivered by a pipeline will occur when the dynamic pressure is approximately 2/3 of the static pressure. The actual flow rate of the water in a hydroelectric system is determined by the diameter of the nozzle.

Pressure Drop in Pipe
(head loss in feet of pipe in PVC Class 160 plastic type pipe)

.	Nominal pipe diameter (inches)
Flow (GPM)	1	1.25	1.5	2	2.5	3	4
1	0.05	0.02	0.00	.	.	.	.
2	0.14	0.05	0.02	.	.	.	.
3	0.32	0.09	0.05	.	.	.	.
4	0.53	0.16	0.09	0.02	.	.	.
5	0.81	0.25	0.12	0.05	.	.	.
6	1.13	0.35	0.18	0.07	0.02	.	.
7	1.52	0.46	0.23	0.07	0.02	.	.
8	1.94	0.58	0.30	0.09	0.05	.	.
9	2.42	0.72	0.37	0.12	0.05	.	.
10	2.93	0.88	0.46	0.16	0.07	0.02	.
12	3.51	1.04	0.53	0.18	0.07	0.02	.
14	4.11	1.22	0.65	0.21	0.09	0.02	.
16	5.47	1.64	0.85	0.28	0.12	0.05	.
18	7.02	2.10	1.09	0.37	0.14	0.05	.
20	.	2.61	1.34	0.46	0.18	0.07	0.02
22	.	3.16	1.64	0.55	0.21	0.09	.
24	.	3.79	1.96	0.67	0.25	0.09	0.04
26	.	4.43	2.31	0.79	0.30	0.12	0.05
28	.	5.15	2.66	0.90	0.35	0.14	0.05
30	.	5.91	3.05	1.04	0.42	0.16	0.11
35	.	.	3.46	1.18	0.46	0.18	0.12
40	.	.	4.62	1.57	0.62	0.23	0.13
45	.	.	.	1.99	0.79	0.30	0.15
50	.	.	.	2.49	0.79	0.30	0.20
55	.	.	.	3.03	1.20	0.46	0.25
60	.	.	.	3.60	1.43	0.55	0.30
65	.	.	.	.	1.66	0.65	0.35
70	.	.	.	.	1.94	0.74	0.40
75	.	.	.	.	2.22	0.85	0.45
80	.	.	.	.	2.52	0.97	0.50
85	.	.	.	.	2.84	1.09	0.60
90	.	.	.	.	3.19	1.22	.
100	.	.	.	.	.	1.36	0.80
150	.	.	.	.	.	1.50	1.60
200	.	.	.	.	.	1.66	2.70
300	.	.	.	.	.	.	5.80
400	.	.	.	.	.	.	9.90

Flow in Gallons per Minute Through Various Sizes of Nozzle Power output of a hydroelectric generator is determined by the pressure of the water at the nozzle and the amount of water flowing out of the nozzle. The larger the nozzle, the greater the flow will be. The nozzle must also be sized small enough to keep your pipeline full and keep the speed of the water in the pipe below 5 feet per second. This table shows water flow through various size nozzles at given pressures. Use it to determine what size nozzle you need to accommodate the flow of water you have and deliver the amount of power you need.
Pressure at the turbine in PSI (Feet = 2.31 x PSI)
Nozzle Size	20	30	40	50	60	70	80	100
1/8"	2.0	2.6	3.0	3.3	3.6	3.9	4.2	4.7
5/32"	3.3	4.0	4.6	5.2	5.7	6.1	6.5	7.3
3/16"	4.7	5.8	6.6	7.4	8.1	8.8	9.4	10.5
7/32"	6.4	7.9	9.0	10.1	11.1	12.0	12.7	14.2
1/4"	8.4	10.2	11.8	13.2	14.5	15.7	16.7	18.7
9/32"	10.5	13.0	14.9	16.6	18.3	19.8	21.1	23.5
5/16"	13.0	16.0	18.4	20.6	22.6	25.1	27.6	31.0
11/32"	15.7	19.3	22.2	24.8	27.2	29.4	31.4	35.0
3/8"	18.8	23.0	26.6	29.6	32.5	35.1	37.6	42.0
13/32"	22.0	27.2	31.2	34.8	38.2	41.3	44.1	48.3
7/16"	25.5	31.2	36.0	40.4	44.4	48.0	50.4	56.8

**QUICK MINI-HYDRO POWER TABLE**
**YOU CAN USE THE FOLLOWING TABLE AS A MEANS TO ESTIMATE APPROXIMATELY**
**HOW MUCH POWER IN WATTS YOU MIGHT EXPECT FROM YOUR WATER SOURCE**
**IF YOU KNOW THE TOTAL HEAD AND THE FLOW RATE.**
**(This table does not apply to submersible hydro generators like the Aquair UW)**
	5	15	20	30	40	50	75	100	150	200	300
Power Output (in watts) Example: 40 feet of head at 30 GPM equals 95 watts of continuous power
	Flow Rate (in GPM)
Head (in feet)
5			5	8	10	15	20	30	40
10		7	12	18	23	30	45	60	80	100
15	5	15	20	30	40	50	75	100	125	150	200
20	8	25	32	50	65	85	125	170	210	275	350
30	12	35	45	70	90	120	180	240	300	400	500
40	16	48	60	95	125	160	240	320	450	600
50	20	60	80	120	160	200	300	400	600
75	30	90	120	180	240	300	450	600
100	40	120	160	240	320	400	600
150	60	180	240	360	480	600
200	80	240	320	480	640
300	120	360	480	720
400	160	480	640