Water Power and Dam Construction - Issue February 2009

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12 FEBRUARY 2009 INTERNATIONAL WATER POWER & DAM CONSTRUCTION

INSIGHT

HI LE wind and solar power

proje cts can be u npre-

dict able because of varia-

tions i n output, tidal power

has long been mooted as one of the few

renewable energy technologies that can be

used to provide a base load for national

power systems. Tides c e rtainly can be pre-

dicted but although developers have been

slow to turn scientific promise int o com-

mercial reality, significant breakthroughs

are now being made. A combination of

comp anies specialising in tidal energy,

large power corporations and govern-

ments kee n on pro moting energy security

and tackl ing climate change are providi ng

the investment that should tur n hypo-

thetic al potential into low carbon power

producti on

Two trends can be discerned. Most pro-

jects involve the deployment of small num-

bers of rel atively s mall scal e t urbines t hat

have already been tested over several years

and which could later be deployed in their

hundre ds t o generate large amounts of

elect ricity at many different locations. A

handful of schemes, most notably in South

Korea, are being develop ed that involve

the installation of large turbines and hun-

dreds of megawatts of generating capacity

in the first instance, uti lising technology

that has been specifically designed for the

project in question.

South Kore a is a prime example of a

country that promote s tidal power in an

effort to boost energy security. With very

little oil, gas o r coal of its own, Seoul has

long relied on imported fe edstock and a

burgeoning nuclear sector to supply the

electricity that powers the thriving econo-

my. Although liquefied natural gas (LNG)

prices have fallen markedly in East Asia in

the past six months, South Korea remains

eager to r educe its dependence on energy

imports through a two pronged strategy of

new nuclear reactors and substantial invest-

ment in renewable energy schemes.

Under Seoul’s Second Basic Pla n for

New & Rene wable Energy Technology

Development and Dissemination, the pro-

portio n of renewab les i n the generatio n

mix is scheduled to increa se from just

1.4% in 2003 to 5% by 2011 and 10% by

2020. While solar power will make som e

contribution towards achieving this target,

large scale tidal power proje cts will

account for t he lion’s share. A tidal power

park is being c reated on the Wando

Hoengg an Water Way, where new tidal

technologies will be tested at the same time

as selling the electricity they produce.

Korean Midland Power Company and

British firm Lunar Energy have already tested

their 1MW, 11.5m turbine in the area and

are currently undertaking a feasibility study

into the construction of a 300MW tidal

scheme at the park, which will require the

installation of 300 turbines by 2015. The tur-

bines will be manufactured by Rotech

Engineering and Hyundai Heavy Industries

and the chairman of Lunar Energy, William

Law, says that the joint venture “will com-

bine the subsea engineering skills of Rotech

with the known fabrication expertise of

Hyundai.”

Another major investor in Wando

Hoenggan is Voith Siemens Hydro Power

Generation, which has taken a 51% stake in

Korea Current Power Joint Venture, along-

side partners Korea Hydro & Nuclear Power

Company (KHNP), renewable power com-

pany Renetec, the government of Jeonnan

Province and South Korean conglomerate

Posco. The joint venture plans to test tidal

power equipment at the site.

However, it is the Sihwa Tidal Power Plant

close to Ansan City on Inchon Bay in

Gyeonggi Province, which is the country’s

best known tidal power project. Developer

Daewoo Engineering & Construction for

Korea Water Resources Corporation

(KWater) expects the project to come on

stream as planned by the end of this year,

when it will become the world’s biggest tidal

scheme with generating capacity of 254MW,

ahead of the 240MW La Rance plant in

France. The total generating capacity is

important but it is the sheer size of the tur-

bines involved that could allow Sihwa to

change the face of the global tidal power

sector. Its ten bulb type 25.4MW turbines are

being supplied by Andritz Hydro as part of

a €75M (US$99.5M) contract that also

includes electromechanical equipment and

engineering services.

Despite the progress that has been made

with tidal power technology in recent years,

it is unlikely that the Sihwa scheme would

be eco nomically viable if it we re not for

$250M of government support and the

obvious environmental benefits of the pro-

ject. In 1994, a 12.4km wall was built to

separate S ihwa Lake from the sea but this

has allowe d waste from industrial opera-

tions on the lake to build up over the past

15 years. By allowing 60 billion tonnes of

sea w ater to enter and then leave th e lake

each year as part of the tidal energy scheme,

it is therefore hoped that pollution will be

removed. T he ten turbines will be located

on the sea wall and will be powered by the

movement of the water between the sea and

the lake, using the head between the high

tide and reservoir levels.

Yet the South K orean national and

provincial authorities remain committed to

exploiting the country’s tidal power poten-

tial, even where such environmental bene-

fits are not apparent. Incheon municipal

authority hopes to develop a muc h bigger

power sch eme by constructing 7.8km of

barriers between four islands close to its

city. It is estimated that this could support

600MW of generating capacity but Incheon

Tidal power primed

for breakthrough

Can tidal power really compete with other forms of

power generation? Neil Ford aims to answer this ques-

tion by investigating what projects are actually being

developed on a commercial basis, and detailing where

future br eakthroughs look likely

The Se aGen turbi ne from Marine Current Turbines

has been tested in Strangford Lough

EDF plans to test its own 3-6MW turbines

in the same area from 2011, follow ing an

assessmen t of the tidal pot ential of sites

along the coast of Brittany.

OpenHydro is also interested in develop-

ing tidal power projects in the nearby

Channel Islands, where interest in tidal

power is even greater. Although British

crown dependencies, the islands of Jersey,

Guernsey, Sark and Alderney lie much closer

to France and so are ideally placed to export

electricity to the European mainland, if and

when tidal power schemes are developed in

heir waters.

In November, the Irish company bought a

20% stake in Alderney Renewable Energy

(ARE), which has a 65-year licence to devel-

op tidal power projects around the island.

OpenHydro has drawn up plans for a

284MW scheme but ARE suggests that there

is 3GW of tidal power generating potential

in total. Brendan Gilmore, the chairman of

OpenHydro, said: “Alderney’s waters con-

tain one of the world’s largest resources of

marine energy. We are delighted to invest in

Alderney Renewable Energy Ltd and to pro-

vide our technology to harness this unique

resource. This resource will deliver security

of energy supply and further economic ben-

efits for the residents of Alderney, and will

provide Europe with long term carbon free

renewable tidal energy.”

The plans are not without controversy,

particularly as the island’s legislature, the

States of Alderney, has voted to shelve a

planned two year pilot scheme in favour of

moving on to the 284MW phase more quick-

ly. Given the lack of commercial track record

for the technology in question, this certainly

INSIGHT

WWW.WATERPOWERMAGAZINE.COM FEBRUARY 2009 13

does not benefit from existing sea walls, so

total construction costs are expected to be

in excess of $2B. A development consor-

tium has yet to be created to pursue the

proposed pr oject and it seems likely that

Incheon council will wish to see the suc-

cessful operation of Sihwa before it com-

mits its own funds.

RENCH CONNECTION

Although La Rance came on stream in 1966,

France made relatively little progress on

xpanding its tidal power sector for several

decades. However, French interest in renew-

able energy seems to have exploded over the

past year, and ambitious plans for new wind,

solar, geothermal and tidal power projects

have been drawn up. According to French

firm Electricité de France (EDF), about 80%

of all European tidal power potential is locat-

ed around the UK and France, so it is not sur-

prising that France is the second biggest

centre for tidal power investment in Europe

after the UK.

EDF has asked potential investors to

submit bids for tidal sch emes that wil l

receive priority connection to the national

grid. OpenHydro of Ireland was unveiled as

the first successful investor in October and

will test its Open Centre turbines, with gen-

erating capacity of 2-4MW each, in the

Paimpol-Breh at region off the co ast of

Brittany. The company hopes that its tech-

nology will overcome a great deal of the

opposition to tidal power projects from

environmenta l groups because they are

mounted on the sea bed and so do not affect

sea views and allow ships to pass overhead.

seems a bold move. However, Gordon

Fitton, the chairman of the Alderney

Commission for Renewable Energy (ACRE),

says that the pilot project is not needed

because of thorough testing at the European

Marine Energy Centre.

ompetition betwe en the various

islands, wh ich are all governed separately,

seems to be driving enthusiasm for tidal

power. Guernsey Electricity is a sharehold-

er, alongsid e EDF and Triodos Bank, in

Marine Current Turbines, wh ich has

alread y tested its 1 .2MW SeaGen turbine

in Strangford Lough in No rthe rn Ireland.

The company is undertaking a thoro ugh

survey of tidal flows around the Bailiwick

of Guernsey, which a UK government

repor t has already concluded has some of

the most a ttractive tidal resources in

Euro pe. The Guernsey company certainly

seems to have a bright future: it was named

the l eading marine power develo per in

Euro pe in a survey by Libr ary H ouse and

The Guardian in September.

Jersey is keen to follow its neighbours’

lead. In December, the Jersey Stat es’ tidal

power steering group concluded that tidal

energy could make “a real contribution” to

the island’s energy security, as well as pro-

viding a new source of income by exporting

electricity. New legislation and an environ-

mental impact assessment on likely projects

are now expect ed. The steering group’s

chairman, Dan Murphy, commented: “We

believe that Jersey’s waters offer an oppor-

tunity for us to harness significant amounts

of renewable energy both for Jersey but also

potentially f or export to European m ar-

kets.” The island is keen to hold talks with

Bird’s eye view of Sihwa tidal plant,

South Korea. Photo courtesy of Daewoo

14 FEBRUARY 2009 INTERNATIONAL WATER POWER & DAM CONSTRUCTION

INSIGHT

the other Channel Islands regarding coop-

eration on exporting elec tricity f rom tidal

power schemes and indeed it would make

commercial sense to develop a shared inter-

connection with the French grid.

RITISH LEADERSHIP

While the Channel Is lands boast some of

the best tidal power potential in Europe,

there are numerous other site s around the

UK that have the potential to turn the coun-

try into the world leader in such technolo-

ies. Indeed, both London and the Scottish

government appear to have grasped the

potential of tidal and wave power, both to

provide low carbon, high security generat-

ing capacity and to create a new hi-tech

sector and much needed employment. In the

early 1 980s, the UK had th e potential to

lead the way on wind power technology but

government support was withd rawn,

enabling German and Danish firms to dom-

inate the industry. London is keen not to

make the same mistake again and is pro-

viding a range of financial incentives to tidal

power investors.

Scotland’s tidal power potential has long

been discussed but it has taken rather too

long to move from optim istic a cademic

research to developing commercially viable

projects. However, the Scottish govern-

ment has steadily provided more financial

suppor t a nd a stri ng of pro jects are now

under development. All are on a small scale

but mo st are being designed wi th rapid

expansion in mind. Estimates published by

the Scottish government suggest that there

is more than 20GW of tidal power poten-

tial along its west coast and around the

islands, f rom the Shetland Islands and

Orkney, down the west co ast to Kintyre

and Galloway.

A development agency, H ighlands and

Islands Enterprise (HIE), is funding a study

by Aquaterr a to survey the tidal potenti al

around Orkney and in the Pentland Fi rth,

and applications for tidal projects have

already been invited. A 2MW turb ine is

being tes ted in the Pentland Firth by

Atlantis Resources Corporation of Hong

Kong. In December, the company

announced that it had signed a memoran-

dum of understanding with CLP Group of

China to develop ti dal power t urbines for

commercial projects, although no financial

details of the deal were revealed. Atlantis

and HIE also plan to set up a central tidal

data centre in Caithness to provide techni-

cal information.

Marine Current Turbines, which was

mentioned e arlier in relation t o Guernsey

Electricity, is confident that its SeaGen tur-

bine will be ready for widespread distrib-

ution in the near future. In December, the

turbine, which produces ele ctricity for up

to 22 hours a day, operated at its maxi-

mum capacity of 1. 2MW for the first time

at the Strangford Lough site, which the

co mpany claim s is “the highest power so

far produced by a tidal stream system any-

where in t he world”.

The managing director of Marine Current

Turbines, Martin Wright, commented:

“Generating at full power is an important

milestone for the company and in particular

our in-house engineering team. It demon-

strates, for the first time, the commercial

potential of tidal energy as a viable alterna-

tive source of renewable energy. SeaGen is

now running exactly as we said it would, but

testing will continue to be carried out, not

only to check SeaGen’s performance over

xtended periods of operation but also to

evaluate how components are standing up to

the harsh conditions and to determine how

the design might be improved.”

While most interest in British tidal energy

is concentrated on western coas ts, some

investment is being made on the North Sea

coast. E xperime ntal units are being tested

near Immingham in the Humber Estuary by

Pulse Tidal that could generate electricity

in areas not ge nerally considered suitable

for tidal schemes. In a statement, the com-

pany a rgued: “Much of the tidal resource

in UK waters and elsewhere is less than

20m deep and is not suitable for technolo-

gies based on rotating turbines . Shallow

sites tend to be closer to shore where instal-

lation, connection and maintenance

become more straightforward than in

remote locations.”

Yet like South Korea, the UK has its own

ambitions for jumbo tidal power projects.

The most high profile potential site is the

Severn Estuary, which has the second high-

est tidal range in the world. A 16km barrier

across the entire estuary has been mooted

that would cost £19.6B-22.2B (US$27.6B-

31.2B) and provide generating capacity of up

to 8.6GW, making it by far the biggest tidal

energy scheme in the world.

However, it is feared that such a structure

would have a detrimental environmental

impact over a wide area of the estuary and

the Severn Basin. Opponents argue that a

more modes t scheme based on a series of

lagoons around the es tuary to be filled at

high tide would be more economical than a

single barrier. The government appointed

engineering fir m P arsons Brinckerhoff to

help assess the various designs and a short-

list of the five most attractive schemes was

published at the end of January (see news

story p5). A three month public consultation

on the five designs is currently underway.

URTHER AFIELD

Elsewhere in the world, tidal power is play-

ing a more modest role in the dash for

renewable s, but there are great hopes for

alternative tidal power technology in Italy.

A 500kW unit is being tested by Fri-El

Green Power in the Straits of Messina,

which separates Sicily from mainland Italy.

When developed on a commercia l scale,

each unit will comprise a floating platform

that is attached to the sea bed and which

has four cables connected to it. Each cable

is kept on the surface of the sea by five

buoys and has five 4m turbines attached to

it that provide 1.2MW generating capacity

on each cable. A spokesperson for the com-

pany said: “These tidal power plants are an

economica l way of pr oducing electri city.

The system is comparatively inexpensive to

build and also to maintain, not least because

it is based on modules, which can also be

easily transported.”

Water speeds in the test area reach 2.5m a

second and change direction every six hours

ut the turbines have been designed to allow

the blades to move 180 degrees to capture

energy in both directions. The company

hopes that its technology can be deployed on

a large scale to provide base load energy,

while in the longer term it expects that it can

be deployed far out to sea. At present, it has

proved uneconomical to locate such devices

more than 100km from the coast but Fri-El

Green Power aims to use electrolysis to turn

the energy produced into hydrogen, which

could then be collected by tanker to be

shipped to the mainland.

The Canadian province of Nova Scotia is

reputed to have the highest tides in the world

and so it is not surprising that it will be home

to Canada’s first commercial tidal power

venture. Three companies, Nova Scotia

Power, Minas Basin Pulp and Power

Company, and Clean Current Power Systems

are to each invest $10-15M in testing their

own turbines in the Bay of Fundy. The chief

executive of Clean Current Power Systems,

Glen Darou, commented: “Tides are better

the farther you are from the equator, so

Canada is in a good position. Tidal energy

really has some special features because the

tides are cyclical, which gives you pre-

dictability. When it comes to energy, that is

very attractive.” The government of British

Colombia is also assessing its tidal potential

on the opposite side of the country, on the

Pacific coast.

It is clear from the wide range of investors

and new proj ects under development that

tidal power is coming of age. It remains to

be seen whether the industry will become a

mainstream element in the generation mix

of any country but technological advances

are bringing pro duction costs down at a

time when governments are becoming

increasingly concerned about energy secu-

rity and fluctuating oil and gas prices. Yet

while power production costs coul d be

competitive with thermal power pla nts on

highly prospective sites such as the Severn

Estuary, the environmental implications of

such major projects will need careful assess-

ment. Smaller scale ventures, particularly

those that do not require barriers overcome

this obstacle but generate electricity at a far

higher cost. The real challenge for the indus-

try will be to demonstrate, as the wind

power sector has done, that mass produc-

tion of a range of different technologies can

bring down produc tion costs to a more

sustainable level.

IWP& DC

16 FEBRUARY 2009 INTERNATIONAL WATER POWER & DAM CONSTRUCTION

GENERATORS

E UW 100 submerged generator has been manufactured

by Ampair for 20 years. It is a three-bladed turbine intend-

ed for use in fast flowing water, requiring zero head, and is

used worldwide to supply battery systems as an alternative

to solar panels or a diesel generator.

The UW 1 00 generates a maximum of 100W of DC current at

12V, 24V, or 48V. The turbine is 312mm diameter and the genera-

tor body is 139mm in diameter which reveals the design’s origin as

suiting a nominal 6in turbine and a nominal 5in generator.

The radial flux permanent magnet generator is housed within a

pressure compensated oil filled cast aluminium casing. The casing is

extremely well sealed, with dual redundant seals throughout, and there

are only two transits into the generator section: firstly for the turbine

shaft and secondly for the electrical cable. The turbine is bi-directional

but because of flow obstruction by the body it is most efficient if facing

into the current.

The electrical output is a four-wire cable carrying AC that is taken

to the external rectifier mounted on a heatsink in a dry location, such

as in a waterproof enclosure or in a suitable building. This rectifier and

heatsink is supplied with the UW as is the first 5m of cable which is a

waterproof marine grade section. Additional cable must be joined onto

this to reach the battery location and the additional cable must be large

enough that the voltage drop is kept within safe and economical limits.

The DC output from the rectifier is ordinarily fed into a battery

bank, often via a battery charge controller. The battery output then

feeds DC loads or a sine wave inverter that supplies 115 or 230V

AC loads. It is necessary to match the turbine voltage to the battery

bank, for example a 12V turbine for a 12V battery bank.

Most users will need to fit a battery charge control regulator to pre-

vent the batteries becoming overcharged and it is strongly recom-

mended that the Ampair regulators are used. Almost all standard solar

regulators are unable to handle the relatively high open circuit voltages

Generating interest under water

The submerged generator from Ampair has

the potential for many applications within

the hydro industry

Left: UW 100 ready for installation in a mill bypass stream, England; Below left:

UW 100 supplied with cable and rectifier; Below right: UW 100 dimensions

213 mm

ø 312 mm

367 mm

from wind or water turbines. This is because a nominal 12V solar panel

will yield approximately 18-20V maximum open circuit voltage where-

as a turbine will yield approximately 100-120V maximum open cir-

cuit voltage. The commercial pressures on solar charge controllers are

such that the input components are not rated for these high open cir-

cuit voltages. This is why Ampair manufacture charge controllers such

as the new Ampair Voyager range which can accept input voltages of

up to 480V for the 48V version of the UW submerged generator.

The cut-in speed of the UW is 1m/sec (2 knots) but Ampair do not

recommend installation below 1.5m/sec because most clients overes-

timate their average water speed. Maximum water speed with the stan-

dard prop is 4m/sec (8 knots) and a low RPM prop is manufactured

for very high water speeds of up to 7m/sec (14 knots). Depending on

water temperature the UW can be oversped without damage.

The UW is ordinarily fitted with a cast aluminium clockwise rotat-

ing turbine. It can also be supplied with an anti-clockwise turbine.

This is only needed if two UW units are mounted on a float and there

are concerns about directional control. Even with two units on a

float the directional stability of the float is ordinarily sufficient that

two clockwise turbines can be used.

HAT ARE THE BEST APPLICATIONS FOR THE

UW?

The UW submerged generator was developed for use in oceanographic

research vessels which need to stream instrumented floats on long tow

lines behind the ships, and need to power scientific equipment and

navigation lights on the floats without running a power cable down

the tow line. The small float area meant that solar panels were inad-

equate and so the users asked Ampair to develop an alternative.

Initially they used the Aquair towed generator which has a 30m

long towed turbine dangling behind and underneath the float. But

this was impractical in shallow waters which is why the UW was

developed as a more compact alternative.

The scarcity of very low-head pico hydro products available on

the commercial market mean that other users have also taken to the

UW generator for use in what Ampair term the ‘land’ market. As

any user of solar or wind will tell you, a 100W generator may not

sound v ery powerful until the 99% capacity factor of the UW is

taken into account, and compared with the very low capacity factor

of small scale solar (typically 10-20%) or wind (typically 5-10%).

In the company’s experience all succ essful UW users are charac-

terised by the following environmental conditions:

• Water velocities in the range 1.5 – 4m/sec (3 – 8 knots).

• Minimum channel size of 320 x 320mm.

• Economically feasible mounting opportunities.

• Short cable runs to a suitable battery location (max 25-50m).

Because of these characteristics the many enquiries from coastal loca-

tions are almost always unattractive. In practice most tidal streams

rarely peak above 3-knots at pier ends which are the only locations

where the cable run constraint can be achieved. Furthermore these

are peak tidal speeds and the daily average tidal speed is typically

only one knot.

WWW.WATERPOWERMAGAZINE.COM FEBRUARY 2009 17

Obviously mountainous areas tend to be hard enough rock to

withstand the erosive flow rates required for success. But even then

the cable length constraint eliminates many high speed mountain-

ous streams because storm events can flood battery houses located

adjacent to the stream bank. If the stream is small enough to remain

within its bank then many streams are simply too shallow.

The most successful land market users tend to be industrial clients

who are already working in the hydro sector and seeking dependable

power for instrumentation such as water quality, water speed, depth,

or fish counters. These tend to be used for reservoir outlet or canal

mid-point monitoring by utilities or environmental and defence agen-

cies. Ampair always recommend installing the UW in conjunction

with solar panels as experience is that in the summer months water

velocity is low and the sun is strong, whilst in the winter the sun is

weak or non-existent and the water velocity is high.

Another client sector that has some success is the domestic user in

the polar regions where there is no sun in mid-winter, and where

they have sm all streams that continue to flow under ice cover.

Obviously mill streams are a possibility but in practice they either

have sufficient head to warrant a head-based generator, or are on-

grid in which case the UW is not economically attractive. Ampair

have built a grid-connected UW but it is not economic at present.

In all cases it is vital that the client constructs a suitable mount-

ing solution. These vary widely to suit the many sites and are entire-

ly at the client’s discretion as this is not an aspect that Ampair can

become directly involved in. Typical mountings are: poles vertically

down into the water, or occasionally vertically up from the bottom;

gantries cantilevered from the bank, often with rigging braces; flow

concentra tors such as culverts that become su bmerged during

floods; and moored floats.

Ampair continues to develop the UW series and in 2008 the tur-

bine hub was upgraded to shroud the seals from damage caused by

fishing line and fine weed. This year the new Ampair Voyager regu-

lator is being released which includes an RS-232 output with battery

monitoring functionality to assist interfacing with SCADA systems.

Further work with the UW series is always being considered but

the investment must be commensurate with the necessarily limited

market size. The company appreciates that the UW has a very low

energy conversion efficiency but that is a necessity of it being an open

stream device – if it had a higher efficiency the flow would stall and

bypass the rotor – and this is a fundamental limitation that restricts

the commercially attractive development opportunities.

Ampair is also taking its first steps into the head-based pico-hydro

market with the HT-series of turbines for grid-connected clients and

for battery charge clients. These are built to order and co ver the

market segment from 6m–20m of head and from 20l/sec – 60l/sec

flow rate. The first is already installed in southeast UK producing

300W into the grid from 6m at 18l/sec which is typical of a small

overshot mill wheel site.

David Sharman, Ampair, Park Farm, West End Lane,

Warfield, RG42 5RH, Berkshire, UK

www.ampair.com

GENERATORS

Above from left to right: UW 100 in a potable water canal, California (photo courtesy PGE); UW 100 mounted vertically in Wales (photo courtesy Environment

Agency); UW 100 cantilevered & stayed – note downstream orientation, Canada

IWP& DC

18 FEBRUARY 2009 INTERNATIONAL WATER POWER & DAM CONSTRUCTION

GENERATORS

realised that my efforts at small scale hydro would be a nice fit with

their work bringing electricity to rural areas in the developing world.

Based in Boston, with field offices in Haiti and Guatemala,

AI DG works to promote green technologie s to underdeveloped

countries and to incub ate small businesses to manufacture these

techno logies. Focused on clean water, clean air, sanitation, and

energy, AIDG seeks to provide services by developing systems that

are affordable to people with modest mean s . Th ey develop clean

burning cook stoves, biodige sters, water filtrati on, wind and

hydroelectric power and solar hot water systems. By incubating

small local businesses to manufacture, maintain and distribute the

systems within the communities that they serve, AIDG offers both

the hope of better services for the underserved and the prospect of

income-generating projects for the businesses that they help create.

In J anuary 2008 I began work with AIDG in Guatemala. The

small community of La Florida in western Guatemala was chosen

as my test site as it had recently lost what little electrical services it

Y INTERES T in small scale

hydroelectricity was born at my

summer home in the Catskills of

upstate New York in the US. My

house is set on several acres with a steep hill

and small waterfall just outside. The waterfall’s

source, a spring high above the house, offered

enough head and flow for a small impulse style

hydroelectric generator. Using an existing cis-

tern formerly used to supply the house, I ran a

2in pipe down the hill achieving a h ead of

about 15m. When I narrowed the aperture at

the bottom of the pipe I ac hieved a strong

steady stream of high pressure water. I was in

business. I still had to build the generator, but

I knew that I had the power to drive it.

After experimenting with several design con-

cepts, I came up with a hydroelectric generator

housed in a five gallon bucket and made almost

entirely from PVC and hardware acquired at

the local home centre. The power was pro-

duced using a permanent magnet alternator

(PMA) driven by a turbine made from PVC

inside the bucket. Made from 8 ¾in, 45 degree PVC couplings cut

in half and mounted on a hub, the turbine had a total of 16 spoons.

To drive the turbine, I created a manifold at the top of the gener-

ator and split the flow into four parts culminating in nozzles arrayed

around the turbine. Thou gh not terribly effi cient, I was able t o

achieve more than the 13.7V necessary for a 12V system. I realised

that because of its simplicity, ease of construction and the fact that

it was relatively cheap to make, the generator might be useful in the

developing world where many communities do not have access to

the electricit y grid. Though I didn’t know it at the time, my new

interest would gain momentum and I began a journey that would

ultimately take me to the highlands of western Guatemala.

EVELOPING POWER

My tenure with an NGO called Ap propriate Infrastructure

Development Group (AIDG) began when I learned of their work. I

Bringing small hydro

to Guatemala

Developing countries are being

hit particularly hard by today’s

economic realities, but small

hydro offers a solution that

makes sense. Sam Redfield

tells the story of one man’s

journey to bring hydroelectric

power to Guatemala

Top, from left to right: A five gallon bucket fitted with metal screen is used as the trash rack at the

top of the penstock; The original factory rotor with the rotor that was designed in Guatemala; Many

people don’t have access to the grid in rural Guatemala but they do use cell phones. Ten Cell phones

can be charged in about an hour, or 240 in a day; Middle from left to right: Mario, a local boy helped

with the installation; After descending a steep hill, the penstock crosses a small road to reach the

generator site; Curious children look on as the bucket generator charges their parents cell phones;

Sam Redfield developed the bucket generator to fill the need for low cost energy in developing coun-

tries; Bottom from left to right: Toyota alternator with factory rotor removed and newly fabricated

neodymium magnet rotor installed; Nozzles used to drive the turbine prior to turbine installation;

Turbine made from 45 degree PVC couplings cut in half and mounted to bucket lid.

had. It also had the abundant water and mountainous terrain nec-

essary for small scale hydroelectricity. The people of La Florida, with

around 100 families, had to travel an expensive and time consum-

ing two hours by bus to a town with electricity to pay a service to

charge their phones.

There are no land lines in these areas and cell phones provide crit-

ical contact with the outside world. They are important economi-

cally as well, as they enable small farmers to seek the best price for

their crops (in this case coffee) and often cut out the middle man.

Also, cell phones have become an important way for people to

transfer money when buying and selling goods. They are a life line

to people in remote areas for contact with family, the market and

medical services.

proposed to install a system at La Florida to charge cell phones.

The challenge was to make the entire installation (generator, pen-

stock, trashrack and associated electronics – regulator, battery and

inverter) cheap enough so t hat the operator of a charging service

would have a reasonable chance of making a profit, while paying

back the cost of the generator and installation over time.

Tying into an existing canal cut into the side of a mountain at La

Florida, we used a five gallon bucket fitted with hardware cloth as

a trashrack. At the bottom of the bucket we plumbed the top of the

penstock and installed a plastic valve for service. With the help of a

local farm boy and machetes prov ide d by the community, we cut

our way through the jungle down the mountain to our generator

site. At close to 60 degrees of incline this was no easy task. Once the

area was cleared we began laying pipe. To secure the pipe, it was

tied off to trees along the route. At the bottom of the initial descent

more pipe w as laid acro s s a relatively flat area and an additi onal

drop in elevation was achieved by crossing a small road and descend-

ing still further into the valley below. In all we laid about 90m of 2in

pipe for a total head of a little more than 29m. At the generator site

we installed another valve for service.

With economy in mind, the system uses only one standard auto-

motive battery. Systems of this size typically use a large bank of deep

cycle batteries that are quite expensive. To make the system afford-

able we would use only one lead acid battery. The battery is never

discharged significantly because the system uses only as much energy

as it can produce in real time. More batteries and greater capacity

can be added later but to put the system in the hands of our con-

stituency it needed to be as cheap as possible. Because the system is

on line all the time, if the load is equal to or less than the energy pro-

duced by the generator, the batt ery is never depleted very muc h,

giving it the same lifespan as if it was in an automobile.

Once the generator was installed, a dump load regulator, battery

and inverter were wired to the generator. After hooking up a couple

of power strips for the phone chargers, we slowly opened the valve

to the generator. Everything seemed to work perfectly. I was getting

a mere 60W, but it was enough energy to charge many cell phones

simultaneously without depleting the battery. My I-pod needed a

bump so it would be the guinea pig. It didn’t catch fire and was fully

charged in short order.

After determining that everything was working well, we gathered

the cell phones from the community. We were able to charge ten cell

phones at a time without discharging the battery. At an average of

an hour’s charging time per phone, if ten phones are being charged

at a time, the system could charge 240 phones in a 24-hour period.

More than enough for La Florida.

Once on site, the entire installation took two people less than a

day to finish. At the time of the installation, the generator cost

around US$350 and a car battery about US$75. We made a dump

load regulator for US$30 and the 100W inverter that we used was

also about US$30. The PVC pipe and valves were expensive at

US$200. With the trashrack, the entire system cost about US$700.

If financed over a one-year period , say 5% interest, the hydro-

electric system would cost US$2 a day in principle and interest. If

the proprietor of such a service were to charge an average of 20 cell

phones a day at 25 cents per charge, that would be a profit of more

than US$3 per day. That is more than US$1000 a year of income. If

one is living on US$6 a day, or US$2190 a year, as many people in

WWW.WATERPOWERMAGAZINE.COM FEBRUARY 2009 19

Guatemala do, US$1000 represents a maj or pay raise and could

make a big difference in someone’s life.

REAKTHROUGH

Since the installation at La Florida we have made some important

breakthroughs. One of the biggest challenges for energy schemes in

the developing world is making systems that are affordable to people

who make almost nothing. At US$700, my system compares well

with equal sized wind and photovoltaic systems, but because our

constituency are under constant economic pressure, the prospect of

incurring a debt of this size is difficult for them to imagine.

The challenge then was to make the generator even cheaper. The

enerator that I developed in the US, though relatively inexpensive

at around US$350, was still a bit pricey. The vast majority of the

cost associated with the generator, the permanent magnet alterna-

tor that I got in the US, was too expensive. Plus there was the cost

of shipping. My thought was to build my own PMA using materi-

als readily available in Guatemala.

I settled on the Nipo Denso alternator from Toyota’s 22R engine

as it is the most common alternator in the developing world. It is

the alternator found in most Toyota light trucks ubiquitous in

Guatemala.

Rebuilding the rotor inside the alternator from scratch, we made a

rotor using neodimium magnets arrayed around a core made from

sheet metal laminates. The core was then attached to a spindle of the

same size as the factory rotor and installed in the alternator. After bench

testing the PMA it proved to be an excellent fit with the rpm’s that I

could achieve with the generator. The cost with labour to manufac-

turing the new PMA was around US$200, about US$100 less than the

cost of the PMA from the US and it could be manufactured locally.

The only element of the generator that could not be sourced in

Guatemala w ere the Neodymium magnets. Though the ma gnets

would have to be shipped from the US, shipping the magnets was a

lot less expensive than buying and shipping the entire PMA, plus the

PMA could be built by locals benefiting the local economy. Xela

Teco, an alternative energy business incubated by AIDG in

Guatemala could build the entire generator including the PMA in

Guatemala. If mass produced the generator could be produced

cheaply and benefit a lot of people.

Ongoing work includes the prospect of creating micro utilities in

which super ef ficient LEDs could be used to light several homes

using the generator. The operator would charge a monthly fee and

make a modest profit while paying back the generator over time.

Another prospect that we are exploring is the charging of small bat-

teries. Used in flashlights and radios, these batterie s represent a

major expense to individuals and blight to the environment when

they are disposed of on the land. Again, the operator would charge

a small fee and both the producer and consumer would benefit.

OOKING FOR PARTNERS

I returned to Guatemala in January 2009 to continue our work

developing small scale hydroelectric power. This year we hope to do

several permanent installations of the generator, training operators

and providing the necessary credit for them to get started.

Developing countries are being hit particularly hard by today’s

economic realities. It is more important than ever to find solutions

to the world’s energy needs and small scale hydroelectricity offers a

clean affordable solution that makes sense. AIDG is always looking

for partners in our endeavours and we welcome any contribution

and support.

If you want to contact AIDG, see what we do, or find out how to

contribute to our work, visit www.aidg.org or contact samred-

field@earthlink.net.

Sam Redfield is a freelance lighting technician for film and

television in New York City, US and volunteers for AIDG

for part of each year.

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