LOTZ Laboratory for sustainable technologies in buildings
Faculty of Mechanical Enginering
University of Ljubljana
ENERESE Training course
Lecture #3
Renewable and low-ex technologies f
energy supply in high energy
efficient buildings
BAT (best available technologies)
for decentralized electricity
production in buildings
Lecturers prof. dr. Sašo Medved,
Note: Some of the pictures in the presentation are used from other sources which are citated. Some pictures are download from web and authors are unknown.
We would like to thank all known and unknown authors. Some schemes are taken from marketing and technical material of different companies to improve the
quality of presentation and we want to make acknowledgment to those companies. This presentation should be used for education purposes only.
Advance technologies for decentralized electricity
production - PV electricity generation
EU directive on “Green electricity” established in 2003, provides legal
basis and targets for electricity production from RES for all EU member
states.
It looks like that one technology, called photovoltaics, benefit mostly
from this directive.
Photovoltaic systems consist of large number of solar cells gathered in
solar panels or modules, convert solar energy directly into electricity
There are several types of solar cells, but they are mostly made from
silicon, very common element on Earth and have similar, but low
efficiency in the range between 10 and 18%.
Despite low efficiency of photovoltaic systems, areas of facades and
roofs in buildings are in most cases large enough for independent
electricity supply. In addition to that, building owners could sell
electricity to the public grid and benefit from so called “feed-in-tariff”
subsidies or other state benefits.
Solar energy
Solar radiation a form of electromagnetic radiation.
Electromagnetic radiation covers a wide range phenomena from radio
waves to x-rays and gamma rays. The sources of those radiation are
different.
The source as in case of solar radiation, is body with temperature above
absolute zero (0K). This is so called thermal radiation.
All electromagnetic radiation travel in vacuum with speed of light, but
differs by wavelength and amount of energy they transfer.
Photovoltaic cell (PV cell)
Most common PV cells are made from silicon.
The cell has two thin layers – bottom one, where small amount of
boron is added to silicon (so called p-type layer with free positive
charged holes) and few mm thick upper layer, where phosphorus is
added to silicon (so called n-type layer because with free negative
charged electrons).
Putting those layers together voltage barrier (~ 0,7 V) rising in PV cell.
n-type sillicon layer
p-type sillicon layer
- + +
junction region as
voltige barrier ~ 0,7 V
PV cell – how electricity is generated
Photons with sufficient energy can produced new electrons and holes.
This results in internal electric field
If resistant load -appliance like bulb or motor - is connected with PV
cell electrons lives the PV cell and travel thought appliance and return
to PV cell where bond together with “waiting” hole. The life of new
electron-hole pair is ended, but appliance produce work in meantime.
current of
electrones I
n-type sillicon layer
p-type sillicon layer
- + +
junction region as voltige
barrier U = ~ 0,7 V
internal
electric
field
applience
Electrical power of PV cell is equal to
Pe = U . I
where U is approximately constant and depends on base material
(mostly silicon) and added atoms (beside P, B also Cd, As,..),
meanwhile electricity current is proportional to the density of solar
radiation.
current of
electrones I
n-type sillicon layer
p-type sillicon layer
- + +
junction region as voltige
barrier U = ~ 0,7 V
internal
electric
field
applience
PV cell – efficiency
The reason why conversion of solar energy into electricity by PV cell is
relatively low (between 15 to 20%) is that only limited amount of
photons of solar radiation has adequate energy to produce new
electron-hole pairs.
For silicon PV cell these are photons with wavelength less that 1,11
mm or having energy greater then 1,18 eV.
Unfortunately entire energy of most photons with adequate energy
can’t be convert into electricity !
Energy of photons (eV)
Density of solar energy
Solar radiation spectrum
Unused photon energy
Energy barrier for Si PV cell 1,11
mm or 1,18 eV
Photons with unsufficient
energy
Wavelenght l (mm)
PV cell – types and efficiency
Mostly used today are silicon PV cell produced
from only one crystal of Si (this type is called
monocristalline “mc-Si” PV cell) of several
crystals of Si (this type is called polycrystalline
“p-Si” PV-cell). This PV cells have highest
efficiency: mc-Si 15 -18% and p-Si 12-16%
Production of Si crystals are expensive and could
be decreased if amorphous Si is used; this is
another form of Si in environment; efficiency of
“a-Si” cells are much lower – up to 8%
Polycrystalline cell can be made from other
materials and could be very thin; this are so
called thin-film PV cell made from cadmium
telluride (CdTe), gallium arsenide (GaAn) or
copper indium deselenide (CIS); they are less
efficient (12 – 14 %) but production is cheaper
mc-Si
p-Si
CIS
PV cell – types and efficiency
Market share of different PV cell technologies
PV cell – types and efficiency
PV cell efficiency (%)
PV cell efficiency (%)
Efficiency of PV cell is independent on solar radiation density (if >100
W/m2), but decrease with cell temperature; that's why researchers try
to combine solar heating (cooling of PV) and electricity production !
Solar radiatin (W/m2)
PV cell temperature (°C)
Photovoltaic modules
For practical reasons PV cell are
encapsulated in PV modules. Modules
are in different size from some hundreds
of cm2 to several m2. Most often
modules in size of 1 m . 1,6 m are used
in buildings. 40 to 50 PV cell are
normally grouped together to produce
20 to 25 V of direct current (DC).
tesnilo
Sealing
zgornje
Glass steklo
enkapsulacijsko
Encapsulate
sredstvo
gel
sončne
celice
Back cover
zadnja
plošča
nosilni okvir
Frame
Each producer declare “peak electrical power (Wp)” for their PV
modules. This is the electrical power when solar radiation is 1000 W/m2
and cell temperature is 25°C. This are ideal conditions and in hour-tohour operation the power is lower (of course 0 W during the night)
Each producer declare “durability factor” for their modules. This is the
guaranteed efficiency after 20 to 30 years of operation. Typically this is
only 5 to 15% -> module having 100 Wp will have power of 90 to 95 W
after 30 years of operation! PV technology is very durable !
PV systems
Two types of PV system are most common:
off-grid systems or island operation stand alone systems
grid connected system
Off-grid system could be low-voltage direct
current (DC) (mostly 24 V) storing electricity in
batteries. Between the batteries and users
inverter could be installed to produce high
voltage (220 V) alternating current (AC). This
allows common appliance to be supplied with
electricity and reduce the size of wires and
reduce system cost.
PV systems
EXAMPLE:
Grid Stand alone PV system with PV modules area of,
inverter and batteries (capacity of 600 Ah). As backup
methanol fuel cell is used.
PV systems
Grid connected system are so called PV solar power
plants. They produce and send electricity to the public
grid. In many countries investors in PV power plant are
encourage with state incentives.
This could be in form of “CO2 coupons” or as “feed-intariff”. Feed-in-tariff is price of electricity offered to
investor in long them contract. Feed-in-tariffs for PV
systems are normally 2 to 4 time greater then regular
price of electricity (between 0,02 to 0,06 €/kWh
depending of country).
Such supporting schemes origin from EU RES-e Directive
published in 1998 bust PV market in last decade.
Largest Slovenian 107 kWp
and EU PV power plant in
Spain (23 MWp) (2008)
Increasing of PV system efficiency
Despite huge volume production
increase of PV systems, the
technological break-through is not
happen yet. Nevertheless there are
ways how to increase annually
produced amount of electricity.
PV modules can be mount on Sun
tracking device. This way annually
production of electricity can increase up
to 60%.
Mirrors with low concentration ration
can be added to PV modules for
increasing the solar irradiation. PV
system electricity production can be
increased by 30% or more.
Integration into the buildings
Mounting the PV modules into the building skin in most cases
reduce electricity production because modules are not installed in
optimal position.
That’s why financial support for such PV systems is higher !
Building integrated PV modules offer many advantages such as:
Modules can replace facade and roof construction and decrease the cost of
building
Modules are weather durable therefore maintenance of buildings can be
cheaper
Modules can improve building envelopment properties – reduce heat
transfer coefficient (U) and provide shading of large glass areas
Guarantee long term income for the owner
Emphases the “green view” of the building
And reduce the use of land for installing PV system
Integration into the buildings
PV modules producers developed solutions to atract architects and
investors. Some examples:
PV modules can be opaque or semi transparent
Density of the solar cell in PV modules can be
custom made adjusted to desired visual effect,
natural lighting, shading.
Source: http://www.dansksolenergi.dk; http://www.concerto-sesac.eu;
http://www.solarpv.co.uk; http://photovoltaic-shingles.com;
http://drexelcorp.wordpress.com
Integration into the buildings
Solar cells can be in different colours to
emphases appearance of the building
PV modules can be integrated in standardized solutions of building
constructions
Source: http://www.dansksolenergi.dk; http://www.concerto-sesac.eu;
http://www.solarpv.co.uk; http://photovoltaic-shingles.com;
http://drexelcorp.wordpress.com
Electricity production – rule of thumb
Rule of thumb
Yearly production of PV system having size of 1
m2 installed in the area with annual global solar
irradiation 1100 kWh/m2 and optimal
orientated position is:
120 – 140 kWh/m2 (for pc-Si modules)
Very often PV modules integrated into the
buildings are not orientated optimal, therefore
reduction factor, shown on the figure, must be
taken into account.
From figure optimal slope and orientation of PV
modules can be seen as well – representing
with red area on the chart ! (Attention: chart is
valid for latitudes between 30°and 50°)
Electricity production – role of thumb
EXAMPLE:
PV system will be installed in city having annual global solar irradiation
1800 kWh/m2. PV modules will be installed on southeast vertical facade.
What will be yearly electivity production with 100 m2 of mc-Si modules?
What will be pre-tax income if “feed-in” tariff is 0,4 €/kWh and what will
be simple return rate if installed kW of PV system cost 3500 € ?
Orientation factor (presented by red dot on previous figure) is 0,65
Annually produced electricity will be:
E ~ 120 kWh/m2 . 1800 kWh/m2a / 1100 kWh/m2a . 0,65 . 100 m2 =
E ~ 12,8 103 kWh/a
Annual income will be: 12,8 103 kWh/a . 0,4 €/kWh = 5120 E
1m2 of PV modules have power of 120 W. Therefore total power of PV
system is 12 kW. Simple rate of return is 12 kW . 3500 € / 5120 E/a = 8,2
years
Electricity production – calculation methods
Public available
computer tool
Site and PV
modules
orientation
Load definition
Electricity production – calculation methods
Operation principle
PV module selection
Follow
recommendations
Iterative
optimization
Environmental issues of PV
Several principles can be used for justify PV systems regarding to their
environmental impact. Here are some examples !
Embodied energy – ratio between produced electricity to energy needed for
production of PV modules versus ; Si cells produce in life time (in general 30
years) 10 to 20 times more energy that it is needed for production
Reduce emissions of greenhouse gases and other air pollutants – emissions
can be reduced between 60 to 90% regarding to energy grid mix
Recycling – not commercial, it is proposed that recycling of Si will reduce
energy consumption to 1/3
More complex method are available – for example PI – pollution index
method (http://envimpact.org) suggested following relations for electricity
production (less is better):
from coal PI = 885; PV PI = 52 , from wind PI = 9 ; from hydro PI = 0,5
The future of PV
The price of electricity produced by
PV system will decrease in next 20
years to the level equal to fossil and
nuclear electricity. This will be
achieved even with today known
technologies.
New development in PV cell
producing will further decrease price
of PV systems
Source: SunWorld
The future of PV
PV will be leading technology in the cities of tomorrow
Source: SunWorld
Intro to other technologies for decentralized electricity production
In this century we will probably face fundamental changes in
energy supply systems. Not only because limited reserves of
fossil fuels, but because wide implementation of decentralized
electricity production in so called smart grid systems.
Example of such systems are so called “micro combined heat
and power generation” (mCHP) systems. High efficiency of
electricity production is established by utilization of waste
heat as by product. Such systems use natural gas or biomass
fuels to generate heat. In most cases combustion engine or
Stirling engine is used to convert heat into mechanical work
for electricity generation.
Intro to other technologies for decentralized electricity production
In addition to the large, hundred and more
meters high turbines, small scale building
integrated wind turbines could supply electricity
to consumers in the building. There are several
technologies, mostly adapted to
low wind velocity in urban areas.
Fuel cells are another technology for combined heat and
electricity generation. Fuel cell combines molecule of
hydrogen and oxygen into molecule of water and generate
free electrons or electricity current. Fuel cell system could
consists reformer which produces hydrogen from natural gas
or liquid biofuel, avoiding problems of storing and
transportation of the hydrogen. High efficiency of electricity
production (up to 45%) and high overall efficiency (up to
90%) without environment impacts is the most important
advantage of this technology.
Intro to CHP (cogeneration)
In principle cogeneration is process of production of electricity in more
efficient way comparing to ordinary thermal power stations.
In thermal power stations vapour (most often water steam) or hot gases
(most often compressed flue gases from combustion chamber)
processes are used to convert heat produced by burning of feed-in fuel
into mechanical work needed to drive electricity generator.
Thermodynamic system that convert heat into
mechanical work is called heat engine.
Theoretical efficiency of heat engine or amount of
internal energy of the fuel that can be converted
into the mechanical work is defined with Carnot
efficiency. In engineering practice, efficiency of
electricity production is lower due to the heat
losses. Part of these losses, related to the heat that
must be transferred from the process into
environment can be use for heating.
In the thermal power stations excess
heat must be transferred to
environment using cooling towers. This
wasted heat can be used for heating of
teh buildings. In this case power plant
operates as cogeneration system.
Intro to CHP (cogeneration)
Because in the large power plants amount of the heat that must be
realised to the environment is much more then the heat demand or the
settlements are to far from power plant, only small part of excess heat
can be used.
More efficient combined heat and power production is possible in
district heating systems, where power generation is adopted to heat
demand during the year. Unfortunately heat supply during the summer
cause high (50% or more) heat losses in distribution system.
This problems can be avoid in case of block-type cogeneration units (or
micro combined heat and power units mCHP) which can be installed in
residential buildings. In most cases they have power up to 50 kW.
Cogeneration
Separate power and heat generation
Efficiency of CHP (cogeneration)
100 kWh
fuel
Power plant
h = 30%
waste heat
waste heat
70,5 kWh
100 kWh
30 kWh
heat
60 kWh
electricity
30 kWh
heat
60 kWh
70 kWh
10,5 kWh
fuel
Boiler
h = 85%
fuel
CHP unit
htot = 90%
waste heat
electricity
10 kWh
Efficiency of CHP (cogeneration)
All year relative heat demand (1)
Efficiency of cogeneration depends on hour-by-hour consumption of heat. CHP
unit should be in operation at least ~ 4000 hours per year to be economical.
Several modules can be combined to avoid operation of cogeneration units at
lower efficiency at partial load.
1
0,8
0,6
Tolerance regarding outdoor temperature
0,4
CHP module 2
0,2
CHP module 1
0
0
DHW heating
1000 2000 3000 4000 5000 6000 7000 8000 8760
h/a
CHP technologies
CHP technologies defer mainly regarding to the process of production of
mechanical work as follows:
internal combustion engine (ICE; Otto or Diesel engine); can use natural gas of
LG, biogas of liquid biofuels; most common used in buildings; high efficiency
(33-40% for electricity production, overall 80 to 100% if condensing technology is
used); in Japan more than 300.000 gas driven units are in operation;
microturbines; are gas engines with electrical power output 30 to 500 kW;
microturbines have lower efficiency comparing to ICE (25 - 30% for electricity
production, overall up to 70%) ; but have better partial-load efficiency, lower
maintenance cost and lower emissions of NOx, CO and hydrocarbons,
Stirling engine; convert heat into mechanical work without any emissions, still in
development
Fuel cells are another CHP technology. Electrochemical process is used for
electricity generation in this devices. Fuel cells will be presented in separate
chapter.
CHP technologies – internal combustion engine
single-cylinder 4stroke 580 cc
engine;
electrical
efficiency 26% to
27%, heat
efficiency 61% to
74% with flue gas
condensing unit;
up to 10 modules
may be networked
and operated via
an integrated
master controller;
Source: http://www.senertec.de/en/derdachs/technology.html
CHP technologies – internal combustion engine
Vitobloc 200 18 kWel/36kWth
4 cilinder gas engine
natural gas driven, biogas, sewer and landfill gas
as option
electrical efficiency 29%, heat efficiency 57%
units up to 401 kWel, 549 kWth
Source: http://www.viessmann.co.uk/etc/medialib/
CHP technologies – internal combustion engine
Source: http://www.viessmann.co.uk/etc/medialib/
CHP technologies – microturbine
Microturbine driven CHP consicts of highspeed generator, comppresor and turbine
wheels that are on the same rotating shaft,
the only moving part in teh enginee. This
enable compact size and long time reliability.
Turbec T100
100 kWel , 155 kWht
natural gas driven
overall efficiency 77%
Source: http://www.turbec.com
CHP technologies – Stirling engine
Stirling engine is so called hot air
engine or external combustion
engine. Mechanical work is
produced by periodic expansion
and contraction of gas (helium)
sealed inside the engine.
Different heat sources can be
used, biomass, solar energy and
geothermal energy are one of
them.
Stirling engine driven CHP are
still under development, pilot
applications with smaller size (1
to 40 kW) with efficiency of
electricity production 10 % to
30% and overall efficiency up to
80 % are in operation.
Solar dish with Stirling
motor driven generator
Pilot Stirling engine
driven CHP; 3 kW Pe,
10,5 kW Pth; heat is
produced burning gases
produced by
gasification of pellets.
Source: http://sunmachine.si/sunmachine_pellet
Economy and environmental impacts
Small scale CHP systems are more expensive per unit of size comparing to
large community scale systems. The cost of combustion driven CHP
systems is between ~ 1200 € to 700 € per kWe (Pe 100 – 5000 kW) and for
microturbine driven CHP systems between ~ 2000 € to 1400 € per kWe (Pe
100 – 5000 kW).
However, the difference in price become lower in recent years. It is
common that small scale CHP systems are included in subsidy scheme for
energy efficient electricity production. In Slovenia, for example, feed-in
tariff for electricity produces by small CHP 23,71c€ per kWhel for the
systems that operates not more than 4000 h per year.
Due to the high overall efficiency, small scale CHP produce much lower
emissions comparing to ordinary fossil fuel power plants – at least 4 times
lower emissions of CO2 comparing to coal fired power plants and more
then twice lower emissions comparing to natural gas fired power plants.
Intro – wind generators
Kinetic energy of wind is
result of solar energy
absorbed on the Earth
surface and rotation of
the Earth.
As any other fluid, air in
lowest part of the
atmosphere, called
troposphere, is driven
by pressure differences
between high pressure
Anticyclone and low
pressure Cyclone
regions.
Utilization of wind energy becomes
most economic technology for
electricity production from
renewable energy sources in recent
years. More then GW of wind
turbines operates in EU and y% of
electricity is produces in EU in this
way today.
Beside large wind turbines, many
producers offer the small turbines,
adapted to the integration in
buildings.
Potential of wind energy
Most often, wind is specified in “windrose” charts. Such chart
presents average yearly wind velocity in certain directions for
selected location at height 10 m above the ground.
S
SSZ
Wind velocity at height h(m) above the ground can be
calculated by eq.:
SSV
4
SZ
SV
3
2
ZSZ
VSV
1
0
Z
Due to the friction between moving air layers, wind
velocity increase from ground level (where w = 0 m/s)
to maximal value at ~ 1000 m above clear space ground.
5
V
ZJZ
VJV
JZ
JV
JJZ
JJV
J
Windrose for City of Ljubljana

 h  m 
v h  v(10m)     
 10   s 
where v(h) (m/s) is wind velocity at height h
(m) above the ground, v(10m) wind velocity 10
m above the ground and  coefficients
dependent on surface roughness (0,1 for
sand surface; 0,13 for pastures; 0,30 for large
settlements)
Wind speed distribution above the ground level for
different surface roughness
Potential of wind energy
Production of electricity by wind turbines can be established only if hour-byhour wind velocities is known. In absence of meteorological data, Weibull
probability distribution be used to calculate probability of wind velocity p(v):
k
k 1
k v
p v     
l l
e
v
 
l
1
If value of shape parameter of distribution k is equal to 2, Weibull probability
distribution converts into Rayleigh probability distribution. If scale parameter
l is equal to:
l
2  v av  m 
  s 
Probability of wind velocity can be calculated base on the average wind
yearly velocity:
2
p v  
 v
e
2
2  v av
 v 
 

4  vav 
1
Potential of wind energy
p(v)
0,45
p(v)
p(v)
0,3
measured
0,4
0,25
vav=2m/s
0,35
Rayleigh
destribution
vav=2.8m/s
v=
0,3
0,2
0,25
vav=4m/s
0,2
0,15
v=
vav=6m/s
0,15
vav=8m/s
v=
0,1
0,1
v=
0,05
0,05
0
0
0
1
2
3
4
5
6
7
8
9 10 11 12 13 14 15
v (m /s)
0
1
2
3
4
5
6
7
8
9
10 11
12
v (m /s)
Example: How many hours per year will wind velocity will be 4 m/2 if average yearly
wind velocity vav is 6 m/s ?
Using diagram on the left, p(v) is equal to 0,12. Number of hours per year when wind
velocity will be 4 m/s is therefore:
 h 
N  0,12  8760  1051 

 year 
Power of wind turbine
Theoretical approach
1
E   m  v2
2
Air volume with mass m (kg) and velocity
v (m/s) has kinetic energy equal to:
 m2 
kg 2  J
 s

If equation id divided by time differential (dt) mass of the air is replaced by
mass flow rate. Considering the continuity equation , relation for wind
turbine power can be developed:
1
1
E
1 m
1
1
E   m  v2
  P    v2   A  v  v2   A  v 3
2
dt dt
2 dt
2
2
m
.V
m
where r is air density (kg/m3), A area of wind capturing (diameter of
the rotor (m2) and v wind velocity (m/s).
It can be seen that wind turbine will produce more
energy at the sea level (since density of the air is 1,225
kg/m3 (25°C, 1 bar) at the sea level and 1.184 kg/m3 at
same conditions at altitude 600 m. In bought cases
wind turbine power depends on cube of velocity.
 kg m2 J

  W

2
s
s s

Power of wind turbine
Theoretical approach
Even in theory, all kinetic energy
could not be transformed
because this results to the zero
velocity behind turbine and
mass flow rate through the
turbine is then zero. Optimal
reduction of air velocity at the
outlet of the turbine define
maximal efficiency which is
called “Betz coefficient” and
have value of 0,597 (59,7%). In
reality efficiency is lower, but
contemporary wind turbine have
efficiency or power coefficient cp
between 38% and 42%.
1
P  cp   A  v 3
2
 kg m2 J

  W

2
s
s s

Power coefficient cp for different wind turbines as
function of speed number l; speed number is ration
between tip rotation speed of the rotor and wind
velocity
Power of wind turbine
Engineering approach
Producers of wind turbines present power diagram for each of their product.
Such diagram shows not only maximum power of the wind turbine, but how
power is related to the wind velocity.
rated power
Wind turbine power (kW)
500
Typical power curve for wind
turbines with cut-in and cutout wind velocities and region
(above 10 m/s) where power of
wind turbine is constant at
maximum value.
400
300
200
100
cut-out velocity
cut-in velocity
0
0
5
10
15
20
wind velocity (m/s)
25
30
Technology of small scale wind turbines
Most common division of wind turbines is regarding to the position of rotation
axe regarding to the wind velocity vector and horizontal axe wind turbines
(HAWT wind velocity vectors are parallel to the rotation axe) and vertical axe
wind turbines (VAWT wind velocity vectors are perpetual to the rotation axe).
Small scale wind turbines could be:
building mounted; smaller wind turbines installed on the roof; often in
size of 1 to 2 kW
pole mounted; free standing and erected in a wind exposed position;
often in size of 5 to 10 kW
Producer: TURBY BV
VAWT
mounted on flat roofs
diameter 2m
hight 3m tall
cut-in velocity 4m/s
Power curve
Technology of small scale wind turbines
Producer: RENEWABLE
DEVICES LTD.
HAWT
cut-in velocity 4m/s
Producer: SOUTHWEST
WINDPOWER INC.
HAWT
diameter 3m
hight 6m tall
cut-in velocity 3 m/s
Producer: NGup
ROTORBLADES
VAWT
Technology of small scale wind turbines
Most small scale wind turbines generate direct current electricity (DC) and
require an inverter to convert it to alternating current electricity (AC). In off-grid
systems battery are needed to store the energy.
Production of electicity
Most simple way to calculate the annual electricity production is using the
capacity factor (CF). This is the ratio of actually produced electricity to
theoretical maximal production per year. Typical capacity factors are between
20 to 40%. CF can be defined as whole year average power of wind turbine:

h
MWh 
E  P  CF  8760 MW  1 

year year 

Example: Wind turbine has diameter of 90 m and power of 3 MW. What will be annual
production of electricity if capacity factor at certain location is 36%. What will be
specific energy production per m2 of device?
 kWh 
 kWh 
9,460,800
E  3000  0,36  8760  9,460,800 
;Espec 
 1487  2


2
year

r
m

year




This is much higher comparing to PV for example !
Production of electicity
Število ur v letu, ko poha veter s hitrostjo v (ur/ leto)
More deatiled calculation of electicity production with wind turbine is based on
three steps:
1200
1000
1. Probability of wind velocity p(v) should be use
for determination of number of operation
hours at different wind velocities for selected location
800
600
400
200
0
2. Power curve of the wind turbine must be
selected.
Moè vetrnice v odvisnosti od hitrosti vetra v (kW)
0
2
4
10
6
8
Hitrost vetra (m/ s)
12
14
16
300
imenska
moè vetrnice
250
200
150
100
vklopna
hitrost
vetra
50
izklopna
hitrost
vetra
0
0
Pridobljena energija pri razliènih hitrostih vetra v (kWh/ leto)
3. The sum of the products between number of
operation hours and power of the wind turbine
at same velocity must be calculated; this sum
represents a total yealy amount of produced
electicity.
4
8
20
12
16
Hitrost vetra (m/ s)
24
2
4
10
6
8
Hitrost vetra (m/ s)
12
28
32
120
100
80
60
40
20
0
0
14
16
Small scale wind turbine cost and environment impacts
Average cost of small wind turbines is 3000 € per kW of rated power
for roof mounted turbines to 4000 € per kW of rated power for polemounted applications. Off-grid systems needs batteries which need
replacing six to ten years. Cost of Pb accumulators is ~ 150 € per kWh
of stored electricity. On-grid systems need inverter at a cost 1000 € ot
2000€.
Environmental impacts which are characteristic for large wind
turbines, such as possible impact on birds, habitats, visual impacts on
landscape, vibration and noise emissions are much less significant in
case of small scale buildings integrated wind turbines, but they all
need to be considered before a turbine is installed.
On the other hand heritage conservation legislation and assessment of
whether the building structure is strong enough to support the weight
of turbine and force of the wind.
Intro to fuel cell (FC)
Electrochemical energy conversion is direct conversion of chemical energy
into electricity.
A device that converts chemical energy into electicity is called fuel cell.
electolite
positive electrode (cathode)
All fuel cells use hydrogen (as fuel) and oxygen (as
oxidant) for operation but they defer regarding to
type of electrodes (solid/fluid) and electrolyte
(fluid/solid).
O2
negative electrode (anode)
Fuel cell is made from two electrodes (- anode and
+ cathode) and an intermediate electrolyte layer, H2
capable to transferring positive ions from negative
to the positive electrode (or negative ions in
opposite direction) but not allowed electrons to
pass thought. Flow of electrons thought external
circuit from negative to positive electrode provides
electrical power of the appliance.
Hydro-oxygen fuel cell
In hydro-oxygen FC hydrogen gas is led to the
porous negative electrode, allowing H+ions to
diffuse thought electrolyte, meanwhile the
electrons anted electrode material and may flow
thought external circuit. If catalyst (platinum film
eon the electrode surface) is present, the H2
dissociate at negative electrode in reaction:
H2
This reaction is accompany with generation of the
water and heat (at temperatures 50 to 800°C
depending on FC type) that can be use for heating.
heat
H+ ions
positive electrode (cathode)
O2  4H  4e  2H2O
O2
electolite
Gaseous oxygen (or air) is led to positive electrode,
where captured bought hydrogen ions and
electrons:
e-
negative electrode (anode)
2H2  4H  4e
R
H2O
Cogeneration system based on PEMFC with natural gas
reformer
Hot water tank
PEFC stack
H2 gas
Air
Air
Backup
water heater
Recovered
heat
Hot water
Fuel processor
Natural gas
Hot water
DC electricity
AC electricity
DC/AC Converter
Source: Tokyo gas
Fuel cells technologies
Examples of large scale pilot PEMFC of different Japan producers
ENEOS celltech
(former SANYO)
TOSHIBA FCP
Natural gas/ LPG
750W
Natural gas/LPG
700W
EBARA
MATSUSHITA
(Panasonic)
TOYOTA
Natural gas
/ Kerosene
1,000W
Natural gas
Natural gas
1,000W
1,000W
Source : NEF Home Page
Fuel cells technologies
Examples of PEMFC cogeneration unit produced by Viewsmann and
scheme of the cogeneration system; natural gas is used as “supplier” of
hydrogen.
Electrical rating power 2 kW;
thermal power 3.5 kW
Source : www.viewsmann.de
Fuel cells technologies
Solid oxide fuel cell (SOFC) use solid ceramic (zircon) as the electrolyte to conduct
oxygen ions at positive electrode. This are high temperature fuel cells (operating
temperature 800°- 1000°C) and have high efficiency of electricity production ~
50%, but can ne up to 80% in the future. High operating temperatures enable
autoreform of several fuels that content hydrogen.
Some other FC are under development as well. For example phosphor acid fuel
cell (PAFC) which use phosphoric acid H3PO4 acid as electrolyte or molten carbon
fuel cell (MCFC) which use molten alkaline carbonate as electrolyte.
SOFC
MCFC
PAFC
Self evaluation
Briefly explain how PV cell produce electricity from solar radiation !
Describe types of solar cells and their efficiency !
Draw U-I curve of photo cell and explain how is dependent on temperature
and density of solar radiation !
What are PV modules ?
What you know about sizing of the PV systems ?
Describe procedure of sizing of the PV systems !
Explain how environment can benefit from PV systems !
Self evaluation
Describe process of cogeneration and explain advantages of cogeneration
Define efficiency of cogeneration regarding to electricity production in
thermal power plant !
Describe technologies of cogeneration !
How wind potential is determined ?
Describe technologies of small wind turbines !
Draw power curve of wind turbines versus wind velocity !
Explain how to calculate yearly produces electricity with small wind turbine !
What are fuel cells and how they work ?
Describe types of fuel cells and their efficiency !
Describe how FC can be used as cogeneration system in buildings !
Literature/References
M. J. Moran, H. N. Shapiro: Fundamentals of Engineering Thermodinamics; John Wiley &
Sons, USA, 1998
Hsieh J.; Solar Energy Engineering, Prentice Press, 1986
Johanson et. All.; Renewable Energy; Sources for Fuels and Electicity, Island Press; 1993
B. Lenz, J. Schreiber, T. Stark; Sustainable building services, Detail Green Books; Germany,
2011
Daniels K., Hammann R.; Energy Design for Tomorrow, Axel Menges, 2008
RETSCreen simulation tool
SunWorld Magazine
SunandWind Magazine
Source: http://www.dansksolenergi.dk; http://www.concerto-sesac.eu;
http://www.solarpv.co.uk; http://photovoltaic-shingles.com;
http://drexelcorp.wordpress.com
References
L.D.D. Harvey; “A handbook on Low-Energy Buildings and District-Energy Systems, Earthscan, UK
2006
B. Sorensen; Renewable energy conservation, transmission and storage; Elsevier, USA, 2007
B. Lenz, J. Schreiber, T. Stark; Sustainable building services, Detail Green Books; Germany, 2011
K. Nishizaki; The Japanese experience in micro CHP for residential use, 2008
K. Daniels, R. E. Hammann; Energy Design for Tomorrow; Edition Axel Menges; Germany, 2008
www.viesmann.de