Micro Hydroelectricity: Benefits and Applications

June 29, 2011

Phil Hofmeyer, Ph.D.Morrisville State Collegehofmeypv@morrisville.edu

Micro Hydroelectricity –BIG energy from SMALLpower systems

Overview

• Basic Electricity» Ohm’s Law, Power Law, power to energy

• Hydro Resource• System Overview• Turbines• Civil Works• Electrical Systems• Permitting

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How I got here…

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How I got here…

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Two nonlinear models fit:

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R2= 0.76

Projected Leaf Area (m2)

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The Training Center – Location

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Primary Energy

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What we really want…

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Basic Electricity

• Electricity is a form of secondary energy• An energy carrier of converted primary energy

to our desired end use» Thermal energy» Mechanical energy» Sound energy» Light energy» Chemical energy

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Basic Electricity

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• Electrical circuit - a network with a closed loop, giving a return path for the current.

A simple electric circuit made up of a voltage source (V) pushing an electric current (I) through a resistor (R).

Conventional flow notation

Ohm’s Law

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OppositionCauseEffect =

REI =

ResistanceVoltageCurrent =

Ohm’s Law and Power Law

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Volts = Amps * Ohms

(volts)

(amps) (ohms)

(power in Watts)

(Volts)(currentIn amps)

Watts = Volts * Amps

Power and Energy

• Energy is the capacity to do work (cumulative)» Common units: kWh, Joules, BTU, therms

• Power is the rate at which work is done (instantaneous)» Common units: Watts, kW, HP, BTU/hr

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Power

Energy

Power and Energy (quick example)

• To convert from power to energy, we must know time of operation

• Assume we have a 1 kW hydro system operating at maximum power and functioning perfectly for 365 days per year

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kWh/yr 8760yrdays 365

dayhours 24kW 1 =

The Hydrologic Cycle

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condensationsublimationInsolation

PrecipitationSurficialflow

Freshwater storage

Transpiration Evaporation

Infiltration

Subsurface flow

Oceanic storage

Groundwater discharge

Local Precipitation Resource

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0

1

2

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Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Prec

ipita

tion

(inch

es)

Average Precipitation for Allentown, PALong-term data from NOAA.GOV

Local Discharge

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Long-term data from waterwatch.usgs.gov

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Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Cubi

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Jordan Creek Discharge (1967-2009)

avg cfs

Local Discharge

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Long-term data from waterwatch.usgs.gov

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Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

Cubi

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Jordan Creek Discharge (1967-2009)

avg cfs1970

Hydrograph – Jordan Creek

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Base Flow?

Long-term data from waterwatch.usgs.gov

Micro Hydroelectricity System Overview

• What is “micro” hydro

• I don’t know. » Many, many definitions and break-downs

• “Small wind” refers to on-site energy consumption (up to ~100 kW)

• Let’s go with on-site consumption (up to perhaps 5 kW)

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Simple DC micro hydro system

Hydro system power output

• Hydro system power output really has only two resource variables to measure

• Head» Vertical Distance between intake and turbine

• Flow» Volume of water per unit time

• Streams tend to be either high head and low flow or low head and high flow

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Measuring Flow – Weir Wall

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Measuring Flow – Float method

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Measuring Flow – Flow meter

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Measuring head – tube and gauge

18 psi

41.6 ft

Great for short penstock runs

2.31 feet

1 psi

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Measuring head – Clinometer and tape

154 ft

16°

X

Sin(16)=X/154

X=42.4’

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Measuring head - Altimeter

978 ft

1052 ft978 ft – 1052 ft = 74 ft

32 psi

Great for very high head systems* how accurate is the altimeter?

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Hydro power (geek math version)

• Epotential = mgh

• Power (watts) = ρQgh» ρ is water density (1000 kg/m3)» Q is flow (m3/s)» g is acceleration due to gravity (9.81 m/s2)» h is head in meters

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V

A

t

ρ

Hydro System efficiency

• Power extraction = ηρgQh» η is system efficiency» Penstock (0.9), turbine (0.9), generator (0.8),

wiring (0.95), and electrical conversion (0.95) efficiency

» 0.8*0.9*0.8*0.95*0.95 = 52% water-to-wire efficiency

» What is residential wind system efficiency?

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Hydro power example

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• A hydro system has 135 feet (41.2 m) of head and 85 GPM (0.0054 m3/s) of useable flow. Assuming typical efficiency, what is the annual energy output expected?

• P = ηρgQh• P = 0.52*1000*9.81*0.0054*41.2• P = 1135 Watts

= 9942 kWh/yr

Wh1000

kWh 1yrdays 365

Dayhours 24 Watts1135

Hydro power (napkin math version)

• To avoid the geek math used thus far, we have an option for quick power estimation…» This is used universally in micro hydro installations

• P (Watts) = Q (GPM) x H (feet) ÷ 10

• From the previous example…• P = 85 * 135 / 10 = 1147 Watts

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Flow examples

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115 GPM (18” culvert)475 GPM

Benefits of hydro power

• If system is sized appropriately, nearly constant power production year-round» More predictable than wind» Much higher site specificity» Downtime for maintenance?

• High system efficiency is possible• Low power systems that generate a lot of

energy

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Turbine selection

• Remember, most systems are either:

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High head, low flowLow head, high flow

OR

Two broad categories of designs

Impulse• Efficient over a wide range

of conditions (most common at high head)

• Nozzles convert potential energy to kinetic energy

Reaction• Designed for medium to low

head sites• Requires high flow rate• Pressure drop occurs with a

draft tube at the runner• More site specific than

Impulse designs

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Impulse designs

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Pelton

Turgo

Reaction Designs

• Francis• Kaplan• Propellor

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Other turbine designs

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• Aquair (zero head)• Darius Turbine

Civil Works

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Intake schemes

Storage• Uses a dam to stop flow• Builds up reservoir • More stable year-round

flow• Siltation• Complex• Expensive• Environmentally difficult

Run-of-River• Diverts part of the stream

flow into a pipe• Little to no flow regulation

throughout the year• Simple• Reliable• Inexpensive• Environmentally friendly

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Run-of-River Intake Placement

• Choose a site with a stable stream bed• The inside of bends accumulate sediment• The outside of bends are subject to erosion

and flood damage• Place the intake along a straight section

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Run-of-River Intake Types

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Coanda screen

Screened box

Settling Basin (Silt Basin)

• Located near the diversion or the intake• Reduction in water velocity• A drain is required for periodic flushing• Turbulence must be avoided

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Penstock Accessories

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Vacuum relief, gate valve, pressure gauge and cleanout

Penstock types

• Most common for small systems is PVC or high density polyethylene (HDPE)

• PVC is cheap, rigid, widely available, and has a low friction coefficient

• HDPE is more flexible, comes in long rolls, more freeze resistant, with slightly higher friction losses

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Watch for Freezing!

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Joining HDPE penstock sections

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Compression Fitting

Heat Fusion

Head Loss Charts

Flow US GPM Pipe Diameter, Inches

1 1.25 1.5 2 2.5 3 4 5 6 8 10

10 2.92 0.87 0.46 0.16 0.07 0.02

20 10.6 3.15 1.63 0.55 0.21 0.09 0.02

30 22.4 6.70 3.45 1.17 0.43 0.18 0.05

40 11.4 5.89 1.98 0.78 0.30 0.09 0.02

50 17.2 8.92 3.01 1.20 0.46 0.14 0.04

60 24.1 12.5 4.21 1.66 0.64 0.18 0.07 0.02

70 16.6 5.61 2.21 0.85 0.25 0.09 0.03

80 21.3 7.18 2.83 1.08 0.32 0.12 0.04

90 8.92 3.52 1.36 0.39 0.14 0.07

100 10.9 4.28 1.66 0.48 0.18 0.07 0.02

150 23.2 9.06 3.50 1.04 0.37 0.16 0.05

200 15.5 5.96 1.75 0.62 0.28 0.07 0.02

250 23.4 9.05 2.65 0.94 0.42 0.12 0.05

300 12.6 3.73 1.34 0.58 0.16 0.05

350 16.8 4.95 1.78 0.76 0.21 0.07

400 21.5 6.33 2.25 0.97 0.28 0.10

Values are feet of head lost per 100 linear feet of penstock (PVC).

Hydro Electrical Systems

• Unlike solar PV and small wind systems, there is no specific section in the National Electrical Code

• Most Codes Enforcement Officers will not be familiar with these systems» Refer to Article 690 (Solar PV), 694 (Small Wind),

and 705 (Interconnected Generators)

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Off-grid micro hydro system

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Grid-tied micro hydro system

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Grid-Tied Electrical Components

1. Energy System and Design Stream Engine 4-nozzle Turgo hydro turbine at 120 VDC (600 Watts, 5 Amps). Earthing equipment ground (6 AWG bare copper).

2. Outgoing source conductors: #12 AWG stranded copper THWN in 1/2” liquid-tight flexible metal conduit. Positive black, negative white, and ground green.

3. Non-fused DC disconnect (250 VDC, 30 Amp) for diversion control isolation. Positive conductor broken.4. Hi-Powered Hydro rectifier and voltage clamp (maximum outgoing voltage 600 VDC). 5. 1200 Watt diversion load (NEC 694.75 requires diversion load to be sized for at least 150% of maximum

turbine output). 6. PV Powered 2000 W inverter with integrated DC and AC disconnects. UL 98 and 1741 listed for grid

interconnection, NEMA 3R for use outdoors. Input 120 to 500 VDC, output 120/240 VAC, split phase, power factor >0.95.

7. Outgoing conductors: #10 AWG stranded copper USE-2. Line 1 black, Line 2 black, Neutral white, and ground green. Conductors sized for 1.5% voltage drop over length of run and ampacity of 4 amps.

8. Easy Read #6 AC kWh meter. GE I-705 120/240 VAC.9. Non-fused AC double pole disconnect (250 VAC, 30 Amp). Hot (line) conductors broken. 10. Easy Read #6 AC kWh meter. GE I-705 120/240 VAC.11. Main distribution panel (200 Amp) in client’s basement. A new double pole (240 VAC, 15 Amp) breaker

is inserted along the bus bar at the furthest point from supply terminals (NEC 694). Maximum allowable renewable energy source breakers total 40 Amps (120% of bus bar rating, NEC 694).

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Permitting

• One of the more difficult portions of micro hydro system installation» And for good reason!

• A bit about New York State» I am unfamiliar with PA regulations

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Interconnection

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Net Metering – New York

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Net Metering - PA

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Department of Environmental Conservation

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Environmental Permitting

• Water resources are usually closely watched and often protected» As they should be!

• Be sure to check local regulations BEFOREstarting a micro hydro system

• Work with the agency, rather than attempting a clandestine hydro system

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Questions?

Thank you!

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