The hydropower scheme in the Alps

Group 18:

Mazin Al Abri

Bartholomew Aloni

Christoforos Katsigiannis

Nikolas Loizou

Artem Lukianov

Hamish A MacDonald

Kingsley Okafor

Contents

Introduction................................................................................................................................................3

Environmental Impact.................................................................................................................................5

Land impact.............................................................................................................................................5

Wild life impact.......................................................................................................................................5

Changing Temperatures..........................................................................................................................6

Methane emissions (from reservoirs)......................................................................................................6

Turbine specifications..................................................................................................................................7

Power......................................................................................................................................................7

Penstock design.......................................................................................................................................8

Available head.........................................................................................................................................8

Design of the turbine.............................................................................................................................10

Improvement.............................................................................................................................................12

Conclusion.................................................................................................................................................14

References.................................................................................................................................................15

Bibliography..............................................................................................................................................15

Appendix...................................................................................................................................................16

Matlab scripts........................................................................................................................................16

Contributions.........................................................................................................................................19

Minutes.................................................................................................................................................19

Brief:

The aim of this project is to design a hydropower scheme in the Alps with a site for a potential

reservoir 750 m above the turbine house of a catchment area of 10 km by 25 km.

IntroductionHydropower plants are one of the most efficient ways of generaing electricity in the world. The hydropower is a reliable source of renewable energy. The hydropower converts the kinetic and potential energy of the water into useful mechanical or electrical energy. Moreover, hydropower plant is known to have high conversion efficiency, which could be over 90%, depending on the type of scheme used. [1]

There are different types of hydropower schemes such as large scheme, pumped-storage and run-of-the-river. In the large scheme hydropower plant, a large reservoir or dam is constructed across a river in order to store huge amount of water. The water is then made to flow through a turbine so as to generate electricity. One of the main advantages of the large scheme is that high capacity turbines could be installed which will generate more flexible power through the whole seasons. Furthermore, this type of hydropower scheme attracts a lot of tourist and it could serve as a location for water sports.

The pumped-storage hydropower scheme uses the excess electricity produced during the off-peak period to pump water into the upper reservoir. This water stored in the upper reservoir is then used to power the turbine during peak time. The pumped-storage plant is one of the best solutions for the power management where the power is generated when needed.[2]

The run-of-the-river schemes use the natural water flowing through the river and elevation drop of the river to power a turbine, which then generates electrical energy. A portion of the river water is diverted through a channel, which leads to a hydropower station, usually located below the actual level of the river in order to provide higher potential energy. The water is then released back to the river. This type of hydropower scheme does not require any large construction; therefore it is cheaper than the other hydropower schemes. [1]

We have decided to construct a large hydropower scheme with a catchment area of 10km by 25km and an elevation of 750km in the Alps due to the design brief.

The hydropower scheme proposed will be

constructed above the Lac de Serre-

Ponçon in the South French Alps. The Lac

de Serre-Ponçon in itself is an artificial

reservoir which is fed by two rivers, the

Ubaye and Durance, and supplies water to

sixteen hydropower stations. The

hydropower scheme we are proposing will

dam the Ubaye River which runs

through the Barcelonnette Basin and create an artificial reservoir with a proposed max surface

elevation of approximately 1650m. This Barcelonnete Basin has a catchment area of

approximately 253m2. This region benefits from consistent inter annual rainfall, especially

during the summer/autumn months where storms can reach approximately 50mm/hour.

Annual rainfall in the region is

typically 733±412mm which,

depending on the drainage

percentage taken, means a

flow rate into the reservoir of

between 1.7 - 4.1 m3/s. The

turbine house for the power

scheme will be located on the

Lac de Serre-Ponçon itself,

approximately 850m below the

new reservoir, and the water will flow back into the Lac de Serre-Ponçon so as to cause minimal

disruption to the other sixteen power stations.

Figure2: Lac de Serre-Poncon and Surrounding Area

Figure 1: Scheme located in South French Alps

Environmental Impact

Land impactBuilding a reservoir requires the use of large land and in flat areas we need much more than

building in hilly areas. Flooding large areas to build reservoirs can result in the destruction of

forests, wildlife habitats, agricultural land, grasslands, marshlands and areas biologically rich.

Also there have been cases where, entire communities had to be relocated, like in the case of

the Three Gorges dam in China.[3]

Wild life impactDammed reservoirs are used for many purposes:

Flood control

Recreation

Agricultural irrigation

We can't claim that every dam is associated with wildlife impacts and hydropower stations.

However, hydropower stations can cause a large impact on aquatic ecosystems because of the

turbine blades that injure organisms and fish. Apart from that ,there can be impacts inside the

reservoirs and at the lower ground of the facility. Reservoir water has bigger amount of

nutrients and sediments due to the fact that the water is more stagnant than normal river

water, thus algae and aquatic weeds be cultivated in excess amounts. These weeds can crowd

other animals and plant life. These should be controlled manually through harvesting or by

introducing organisms and fish that eat such plants.

In addition, if big amounts of water is stored behind

the reservoir, segments of the downstream river will

dry out. This is a usual phenomenon in hydropower

stations and for this reason is necessary for the

operators to release amounts of water at certain

times of year. Also reservoir water is low on

dissolved oxygen levels, thus when released there

can be a negative impact on downstream plants and animals. Aerating turbines can be installed

to increase the amount of dissolved oxygen in the water.[3]

Changing TemperaturesTemperature is another issue we have to deal with. Rivers are fairly homogenous in

temperature, whereas reservoirs are layered, meaning they are warm at the top and cold at the

bottom. When water is released downstream, it is usually from the bottom of the dam,

meaning that the river water will now have a change in temperature. Many micro organisms

depend on a regular cycle of temperatures and by changing that we can affect their life cycle if

not kill them.

If the dam is allowed to release water from its reservoir, it will often do so only once in a while,

release small floods. This leads to scouring and armoring of the riverbed. The high energy of the

sudden floods picks up and removes smaller sediments like silt, sand, and gravel, as well as

aquatic plants and animals, leafy debris, and large woody debris. By this, sets of habitats are

erased and also the riverbed below the dam becomes like a pavement of cobbles and loses its

value as a habitat for plants and other organisms.

Methane emissions (from reservoirs)The reservoir of water for hydroelectric power station releases into the atmosphere a big

amount of methane and dioxide.Carbon emissions vary from dam to dam but despite that

emissions are still in high levels.This is because plants and trees in them start rotting and

decompose by other method without the use of oxygen.So this kind of decomposition release a

great amount of carbon and methane in atmosphere which increase pollution.[4]

Turbine specifications

PowerAccording to the area specifications:

Catchment area – 23 x 11 = 253 km2

Average rainfalls – 733 mm per year

Therefore, if there is no drainage, the average collected volume is:

V=253×0.733=185.4×106m3

There are 365 days in one year, 24 hours in one day and 3600 seconds in one hour. Of these,

we can calculate the average volume flow rate: Q= 185.5×106

365×24×3600=5.88m3 /s

With the drainage 30-70% the flow rate might vary 1.7 - 4.1 m3/s respectively.

The level difference between turbine and reservoir is: H = 875 m.

From these data the average generated power can be calculated:

P= ρgHQ=50.47 MW

The energy potential: E=ρgHV3600

=442GWh

The installed capacity is 495MW and the load factor is 50.47495

×100 %=10.1 %.

The power depends on the volume flow rate, which depends on the rainfalls. This is

represented on the following graph:

Penstock designAssuming the slope of the mountain is at an angle of 20° then the approximate length of the

penstock can be found: ¿H

sin 20=2558m , where H = 875 m

The diameter of the penstock can be found using ‘findD’ function in Matlab (Appendix 1).

The function is recursive and gives the diameter of 3.293 m.

However, the real condition might vary slightly and, due to safety issues, it is better to choose

the actual diameter slightly bigger, for example, 3.3 m.

Due to the fact that, Pelton wheel does not require specific dimensions for the tail race, it was

reasonably approximated to make it 50 m long and with the same diameter 3.3 m as the

penstock.

Available headThe level difference between reservoir and the turbine is 875 m. However, due to frictional losses in the pipe the actual head is less and called available head.

The available head can be found using the following formulas.

First, we need to find the cross-sectional area of the penstock:

A=π D2

4=8.55m2

Then we can find velocity of the water at the maximum flow rate of 70 m3/s

V=QA

=8.17m /s

Now we can find the dynamic head:

H d=V 2

2g=3.4 m

And the head loss:

H L=( 4 fLD

+K )×H d=43m

Where K=5 and f is friction factor, which can be found from the Moody diagram using the surface roughness ε d = 1×10−4.

Of these, available head can be obtained:

H=Z−Hd−H L=828.6m

Where Z is the original level difference, which is 875 m in our case.

The following graph represents different heads depending on the flow rate:

The ratio of the available head to the level difference depending on the flow rate is shown on the following graph:

Design of the turbineDue to the high level difference (875m), the Pelton turbine has been chosen for this scheme. Other turbines such as Francis or Kaplan are able to work with heads below 300 m and even lees.

The installed power capacity is 495 MW which splits between three turbines - 165 MW each.

There are 6 jets in each turbine, 55MW per jet.

The specific speed of the turbine can be found using:

K N=ω √ Ph

ρ(gH )5 /4 =0.112

where ω is rotational speed in rad/s, ω= rpm30

∗π (rad/s)

The generator consists of 6 pole pairs, then the turbine should rotate at the speed of 500 rpm in order to provide 50 Hz.

Using this formula the desirable rotation speed can be found: f T=fnp

The efficiency of the power scheme can be found using:

η= PPH

×100 %

where P = 495 MW, PH=ρgHQ=568.5MW

Therefore the efficiency of the hydropower scheme is:

η= PPH

×100 %= 495568.5

×100 %=87%

The following graph shows efficiencies of different turbines including Pelton turbine:

And this graph shows the comparison real and ideal efficiencies:

The ideal efficiency can be found using:

η=2× ¿

where θ can be taken as a standard blade angle - 165°

The jet velocity can be calculated using:

V j=0.98×√2gH=125m /s

where 0.98 is velocity coefficient

The velocity of the blades is: U=V j

2=62.5m /s

Jet diameter can be found from the cross-sectional area of the jet:

A j=Q j

V j=0.03m2

And then the diameter:

D j=√ 4 A j

π=0.199m

Optimum wheel diameter can be found from:

Dw=V j

ω=2.39m

ImprovementA lower dam could be constructed in the river which leads to the lake. The dam could be used

as a pump storage by using Francis turbines at the lake. The water from the lake could be then

pumped to the lower dam when the excess power is available or at lower cost. The pumped

water is then released to drive the Francis turbines as shown in Figure [1].

Figure 1

The pumped-storage plant can be used to cover the high demand of the electricity when it is

required, especially in the summer at the lowest power generation for the Pelton wheels.

Another improvement which can be made to improve the power output and efficiency of system

is by introducing the Turgo turbine to the system or replacing Pelton wheel with Turgo Turbine.

The Turgo turbine is a simple impulse turbine (more like a modified Pelton Wheel) with a higher

specific speed compared to the Pelton.[5]

The design of the Turgo turbine allows a larger jet of water to be directed into the runner at a

particular angle. This is what increases the specific speed and thus a higher power output, most

of all higher efficiency. In terms of reliability, the Turgo turbine requires minimal maintenance

and most are designed to withstand worst case scenarios. [5]

When operating on a very high wave of water containing particles, the effect is very low on

Turgo turbine. The runner profile and jet of water are very important to maintain high

efficiencies. Wearing of material does occur, but this wearing is small and uniform across the

runner profile of the Turgo turbine therefore leaving the turbine with a very little effect on the

performance.[6]

ConclusionWe have designed a large hydropower scheme in the Alps, which has an average power output of 50.47MW. Due to the size of the reservoir, it has the potential of generating up to 442GWh of electricity with an efficiency of 87%.

Hydropower plants offer various benefits to the society. These benefits range from job creation to tourist attraction in the nation where they are located. Additionally, Large hydroelectric schemes can be used in flood control and for agricultural irrigation purposes. Large hydropower

reservoirs can serve as a ground for recreational and transportation purposes, thereby, contributing immensely to the growth of the economy.

Finally, the construction of pumped-storage hydropower scheme below the main reservoir appears to be very viable and efficacious when it comes to electricity generation as it ensures that flexible and reliable electricity, which meets the shifting demands of the consumer is generated at all time.

References[1] A. Kumar, T. A. Schei, 2009, Contribution to Special Report Renewable Energy Sources (SRREN), Hydropower, chapter 5, available at: http://cms.srren.ipcc-wg3.de/report/srren-drafts-and-review/fod-drafts/fod-chapter-05.pdf/view [last Accessed 26/03/15].

[2] US DEPARTMENT OF THE INTERIOR, 2005, Hydroelectric Power, available at: http://www.usbr.gov/power/edu/pamphlet.pdf [last Accessed 26/03/15].

[3] Y. Zhong,G. Power,1996, SOME ENVIRONMENTAL IMPACTS OF HYDROELECTRIC PROJECTS ON FISH IN CANADA, available at http://www.hardystevenson.com/Articles/SOME%20ENVIRONMENTAL%20IMPACTS%20OF%20HYDROELECTRIC%20PROJECTS%20ON%20FISH%20IN%20CANADA.pdf [last Accessed 25/03/15].

[4] Union of Concerned Scientists ,N/A, Environmental Impacts of Hydroelectric Power, available at: htp://www.ucsusa.org/clean_energy/our-energy-choices/renewable-energy/environmental-impacts-hydroelectric-power.html#bf-toc-1 [last Accessed 26/03/15].

[5] GILKES. (2015, MARCH 15). HYDROPOWER. Retrieved from GILKES.COM: http://www.gilkes.com/Turgo-Turbines

[6] Gordon, G. G. (2015). GILKES TURGO IMPULSE HYDRO TURBINEGILKES TURGO IMPULSE HYDRO TURBINE. Kendal Cumbria: Gilbert Gilkes & Gordon Ltd.

BibliographyFearnside, Phillip M. 1989. Brazil's Balbina Dam: Environment versus the legacy of the Pharaohs in Amazonia. Environmental Management, July/Aug 1989, Volume 13, Issue 4, pp 401-423.

National Renewable Energy Laboratory (NREL). 2012. Renewable Electricity Futures Study. Hand, M.M.; Baldwin, S.; DeMeo, E.; Reilly, J.M.; Mai, T.; Arent, D.; Porro, G.; Meshek, M.; Sandor, D. eds. 4 vols. NREL/TP-6A20-52409. Golden, CO: National Renewable Energy Laboratory.

Yardley, Jim. November 19, 2007. Chinese Dam Projects Criticized for Their Human Costs. New York Times.

National Renewable Energy Laboratory (NREL). 2012. Renewable Electricity Futures Study.

IPCC, 2011: IPCC Special Report on Renewable Energy Sources and Climate Change Mitigation. Prepared by Working Group III of the Intergovernmental Panel on Climate Change [O. Edenhofer, R. Pichs-Madruga, Y. Sokona, K. Seyboth, P. Matschoss, S. Kadner, T. Zwickel, P. Eickemeier, G. Hansen, S. Schlömer, C. von Stechow (eds)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA, 1075 pp. (Chapter 5 & 9).

National Academy of Sciences. 2010. Electricity from Renewable Resources: Status, Prospects, and Impediments. Washington, DC: The National Academies Press. Online at http://www.nap.edu/openbook.php?record_id=12619

[IPCC, 2011: IPCC Special Report on Renewable Energy Sources and Climate Change Mitigation.

Appendix

Matlab scripts

disp('Hydro Power Scheme in Alps')Z = 875; %elevationangle=20;Q = 70;% Maximum volume flow rate (approximate estimation)L = Z/sin(20*pi/180);%L2 = 40;Kh = 5;rho=1000;g=9.81;nt=3;HL = 0.05*Z;% a head loss of 10% of the elevation% Case of a single pipe% typical parameters chosesed = 1e-3; % Surface roughnessD0 = fzero(@(D) findD(D,Q,ed,HL,L), [0.1 10]);D= ceil(D0*10)/10;% round upt the diameter to the nearest 100 mmdisp(['The minimum diameter of the penstock is ', num2str(D0,5),' m; so let''s take a diameter of ', num2str(D,'% 4.2f'),' m'])PH= rho*g*Z*Q;Qh= 0:70;nth = nt*6;Qnh= 23.3/6;Pnh= 165e6/6;rpmh= 500;[Hh, KNh, effh] = turbine_spec(Qh, Z, L, D, Kh, nth, Qnh, Pnh, rpmh);display(['Available head= ',num2str(Hh,4),... ' m; Specifc speed KN per jet= ', num2str(KNh,3),... '; Specifc speed per turbine= ', num2str(sqrt(6)*KNh,3),... '; Specifc speed total= ', num2str(sqrt(nth)*KNh,3),... '; efficency= ', num2str(100*effh,'%3.0f'),' %']);VJ=0.98*sqrt(2*g*Hh); % Jet velocity, assuming a velocity coefficient of 98%disp(['Jet velocity = ', num2str(VJ,3), ' m/s'])AJ=Qnh/VJ; % Jet areaDJ= sqrt(4*AJ/pi); % Jet diameterdisp(['Jet diameter = ', num2str(DJ,3), ' m'])DPW = VJ / (rpmh/30*pi); % Optimum Wheel diameterdisp(['Wheel diameter = ', num2str(DPW,3), ' m'])theta = 165;Ub=VJ/2;efftheor= 2*Ub/VJ*(1-Ub/VJ)*(1-cosd(theta));

turbine_spec function

function [Hn, KN, eff] = turbine_spec(Q, Z, L, D, K, nt, Qn, Pn, rpm);rho= 1000; g= 9.81; ed= 1e-4;A= pi*D^2/4;V= Q/A;Hd= V.^2/2/g;HL= (4*fmoody(Q,D,ed)'*L/D+K).*Hd;H= Z - Hd- HL;%figure(1);plot (Q, H/Z*100,'linewidth', 2); grid on;set (gca, 'fontsize', 20);xlabel('Q (m^3/s)'); ylabel ('H/Z %');%figure(2)plot(Q, H, 'k-', Q, Hd, 'b--', Q, HL, 'r-.','linewidth', 2);grid on;set (gca, 'fontsize', 20);xlabel('Q (m^3/s)'); ylabel ('H (m)');legend('Available head','Dynamic head','Head loss','Location','W');%Pe = 0.96*rho*g*H.*Q;figure(3)plot (Q, Pe/1e6,'linewidth', 2); grid on;set (gca, 'fontsize', 20);xlabel('Q (m^3/s)'); ylabel ('P (MW)');rad= rpm/30*pi;Qt= nt*Qn;Hn = Z - (1 + 4*fmoody(Qt,D,ed)*L/D+K)*Qt^2/A^2/2/g;KN = rad*sqrt(Pn/rho)/(g*Hn)^(5/4);A= pi*D^2/4;V= Qt/A;Hd= V.^2/2/g;HL= (4*fmoody(Qt,D,ed)'*L/D+K).*Hd;H= Z - Hd- HL;eff= Pn/(rho*g*Hn*Qn);

findD function

function f = findD(D,Q,ed,HL,L)f = 4*fmoody(Q,D,ed).*L./D * 8.*Q.^2/9.81/pi^2./D.^4 - HL;

fmoody function

function f= fmoody(Q,D,ed,nu)% Calculates the friction factor for the Moody diagram% from either the volume flow rate, the pipe diameter, and the roughness% Input format fmoody(Flow rate, Diameter, roughness, kinematic viscosity% Viscosity is optional: default value for water: 10^-6

% Roughness optional; default value 10^-6% or from the Reynolds number and the relative roughness% Input format fmoody(Reynolds number, [], relative roughness)% Relative roughness is optional: default 0.001if nargin()<4, nu= 1e-6; endif nargin()<2, D=[]; end;if isempty(D), % all input is already nondimensional Re= Q; if nargin()<3, ed= 1e-3; end; e= ed;else A= pi.*D^2/4; U= Q./A; Re= U.*D/nu; if nargin()<3, ed= 1e-6; end; e= ed./D;endf= zeros(length(Re), length(e));idx= find (Re<=2300);if length(idx), f(idx)= 16./Re(idx); end;idx= find (Re>2300);if length(idx), f(idx)= colebrook(Re(idx),e)/4; end; %-------------------------------------------------------------------------function f=colebrook(Re,e)% Colebrook Equation% f = Darcy-Weisbach friction factor% R = Reynolds number% r = relative roughnessf=zeros(length(Re), length(e)); for i=1:length(Re) for j= 1: length(e) % First part of Serghides equation to find first guess f0 = 0; f1 = -2*log10(e(j)/3.7+12/Re(i)); while abs(f1-f0)/f0 > 1e-5; f0= f1; f1= (2*log10(e(j)/3.7+2.51/Re(i)/sqrt(f0)))^-2; end f(i,j)=f1; endend

Contributions

Introduction, diagram - Mazin Al AbriEnvironment - Nikolas Loizou and Zak RaziLocation and planning - Hamish Anthony MacDonaldTurbine selection, calculations - Artem LukyanovImprovements - Mazin Al Abri and Okafor VicktorConclusion, corrections and checking - Bartholomew Aloni and Hamish Anthony MacDonald

Minutes25/02/15

Everybody was present

Discussed about the project Had some thoughts about possible hydropower schemes Split the research areas of the project

5/03/15

Everybody was present

Discussed what we have researched Found the suitable location Started to locate parts of the scheme

17/03/15

Everybody was present

Turbine has been selected Calculations have been done Environmental effect has been estimated Started preparation for the presentation The slide preparation process was split between memebers

20/03/15

Everybody was present

Final preparation before the presentation Everything was checked and corrected