supply of a house using hybrid wind-solar power system Tams Beke - - PowerPoint PPT Presentation

Simple model for the energy supply of a house using hybrid wind-solar power system

Tamás Beke Our Lady Catholic Grammar School Kalocsa, Hungary Eötvös University Physics Education PhD Program

2

Research project for secondary school students

• The problem to be solved is whether and how

a typical house can be supplied with energy

• ff-grid, based entirely on renewable energy

sources.

• To this end our students carried out a long

term measurement series in order to assess typical energy consumption of houses.

3

• 1. Introduction
• Renewable energy sources are becoming

increasingly important in energy supply.

• Their contribution covered an estimated 19%
• f the global final energy consumption in 2011

[1].

• They may not completely substitute fossil

fuels and atomic energy in the near future, yet they offer an attractive alternative in the long term.

4

Solar and wind energy

• Among renewables, solar and wind power are

widely available on the Earth.

• The locally available solar energy and wind

power substantially depend on meteorological conditions and are highly variable in time.

5

• Due to their significance and perspective, it is

desirable to give renewable energy sources an appropriate share in physics teaching.

• In this lecture a related research project

designed for and accomplished by secondary school students is presented.

6

1st stage

• Our ‘Renewable energy sources: stand-alone

house with hybrid wind-solar power generator’ project has been carried out in three stages.

• For the first stage the daily energy

consumption of an average house was investigated.

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2nd and 3rd stage

• For the second stage a mathematical model

for an off-grid house with hybrid wind-solar power generator and accumulator system was developed.

• For the third stage a computer simulation

program was developed, based on the mathematical model and the data collected by students.

8

• Wind power has significant variation over

shorter time scales therefore it is used generally in conjunction with other sources to give a reliable supply.

9

• 2. Gathering data
• All the students taking part in this project live

in the same town, Kalocsa, in self-contained detached houses with insulated walls and central heating systems.

• The number of student houses was N=31.

10

• We monitored the temperatures on every day

during the project.

• I have chosen 4 days from 4 different seasons

to present the data: –the ‘winter day’ is 2014-Jan-1, –the ‘spring day’ is 2014-Apr-1, –the ‘summer day’ is 2014-Jul-1, –the ‘autumn day’ is 2014-Oct-1.

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Outside temperatures

• We can see in figure 1 the outside

temperatures on the days chosen.

Temperature (2014-Jan-1)

1 2 3 4 5 6 7 0:02 2:02 4:02 6:01 7:54 9:45 11:45 13:45 15:45 17:45 19:45 21:45 23:45 time T [°C]

Temperature (2014-Apr-1)

5 10 15 20 25 0:00 2:00 4:00 6:00 7:54 9:54 11:54 13:54 15:54 17:54 19:54 21:55 23:55 time T [°C]

Temperature (2014-Jul-1)

5 10 15 20 25 30 0:01 2:02 4:02 6:01 7:58 9:58 11:58 13:58 15:59 17:59 20:01 22:01 time T [°C]

Temperature (2014-Oct-1)

5 10 15 20 25 0:01 1:55 3:55 5:53 7:50 9:46 11:45 13:45 15:49 17:45 19:44 21:42 23:36 time T [°C]

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Energy consumption

• Students collected the data of the daily energy

consumption of their own houses:

– the energy consumption of the electric appliances was monitored; – the natural gas consumption was monitored by gas meter; – the wood and coal burned in furnaces were measured in weighing-machines (scales).

,

1 , , ,





  

N j j j j i total ave ave i total

N A E N N A E

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• The ‘heating season’ spans from 1st October

to 15th April; between 16th April and 30th September the period was designated as ’non-heating season’.

• The average daily electricity consumption of

students’ household was circa:

– 37 MJ in the heating season – and about 35 MJ in the non-heating season.

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• 3. Modelling
• Now a model of an off-grid hybrid wind-solar

power generating system is presented.

• In this model we assume that the users

cannot (or do not want to) rely on the electric grid system, therefore the energy produced by the hybrid wind-solar system is stored locally in accumulators.

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Model setup

• The model setup is depicted schematically in

figure 2.

• The parts of the system are the power

generating system (photovoltaic modules and wind turbines), the energy storage unit.

16

PV modules and wind turbines

• This off-grid hybrid wind-solar power

generating system consists of Nphotov pieces of PV modules and Nwindt pieces of small wind turbines.

17

PV module

• A photovoltaic (PV or solar) cell converts the

energy of light directly into electricity by photovoltaic effect.

• In a PV cell the direct conversion of light to

electricity occurs in semi-conducting materials.

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Power of a photovoltaic module

• The power of a photovoltaic module (Pphotov) is

proportional to the incoming light power [2]:

   ,

t I A η = t P = P

photov photov photov photov

 

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Power of one PV module

• Figure 3 shows the power of one photovoltaic

module on the days chosen.

Power 1 solar module (2014-Jan-1)

2 4 6 8 10 0:02 2:02 4:02 6:01 7:54 9:45 11:45 13:45 15:45 17:45 19:45 21:45 23:45 time P [W]

Power 1 solar module (2014-Apr-1)

20 40 60 80 100 120 140 0:00 2:00 4:00 6:00 7:54 9:54 11:54 13:54 15:54 17:54 19:54 21:55 23:55 time P [W]

Power 1 solar module (2014-Jul-1)

40 80 120 160 200 0:01 2:02 4:02 6:01 7:58 9:58 11:58 13:58 15:59 17:59 20:01 22:01 time P [W]

Power 1 solar module (2014-Oct-1)

20 40 60 80 100 120 0:01 1:55 3:55 5:53 7:50 9:46 11:45 13:45 15:49 17:45 19:44 21:42 23:36 time P [W]

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Energy of PV module

• In figure 4 the sum-total electrical energy produced

by one photovoltaic module on the days chosen is shown.

Energy 1 solar module (2014-Jan-1)

0,02 0,04 0,06 0,08 0,1 0,12

0:02 2:02 4:02 6:01 7:54 9:45 11:45 13:45 15:45 17:45 19:45 21:45 23:45 time E [MJ]

Energy 1 solar module (2014-Apr-1)

0,5 1 1,5 2 2,5 0:00 2:00 4:00 6:00 7:54 9:54 11:54 13:54 15:54 17:54 19:54 21:55 23:55 time E [MJ]

Energy 1 solar module (2014-Jul-1)

1 2 3 4 5 0:01 2:02 4:02 6:01 7:58 9:58 11:58 13:58 15:59 17:59 20:01 22:01 time E [MJ]

Energy 1 solar module (2014-Oct-1)

0,5 1 1,5 2 0:01 1:55 3:55 5:53 7:50 9:46 11:45 13:45 15:49 17:45 19:44 21:42 23:36 time E [MJ]

 

, T + ith Δt N t P = E

day day day ith photov photov i photov



 

,

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Wind turbines

• Wind turbine generates electricity from the kinetic

power of the wind.

• The power output of the wind turbine is proportional

to the area swept by the blades and to the cube of the wind velocity.

• The power of wind turbine (Pwindt) is assumed [3]:

     ,

t v A 2 t ρ C = t P = P

3 wind rotor air po windt windt

  

22

Power of wind turbine

• In figure 5 the power of one small wind turbine

can be seen on the days chosen.

Power 1 small turbine (2014-Jan-1)

10 20 30 40 0:02 2:02 4:02 6:01 7:54 9:45 11:45 13:45 15:45 17:45 19:45 21:45 23:45

time

P [W]

Power 1 small turbine (2014-Apr-1)

20 40 60 80 100 0:00 2:00 4:00 6:00 7:54 9:54 11:54 13:54 15:54 17:54 19:54 21:55 23:55

time

P [W]

Power 1 small turbine (2014-Jul-1)

20 40 60 80 100 120 140 160 0:01 2:02 4:02 6:01 7:58 9:58 11:58 13:58 15:59 17:59 20:01 22:01

time

P [W]

Power 1 small turbine (2014-Oct-1)

5 10 15 20 0:01 1:55 3:55 5:53 7:50 9:46 11:45 13:45 15:49 17:45 19:44 21:42 23:36

time

P [W]

23

Energy of wind turbine

• In figure 6 the sum-total electrical energy produced by
• ne small wind turbine on the days chosen is shown.

Energy 1 small turbine (2014-Jan-1)

0,0 0,1 0,2 0,3 0,4

0:02 2:02 4:02 6:01 7:54 9:45 11:45 13:45 15:45 17:45 19:45 21:45 23:45 time E [MJ]

Energy 1 small turbine (2014-Apr-1)

0,0 0,2 0,4 0,6 0,8 1,0

0:00 2:00 4:00 6:00 7:54 9:54 11:54 13:54 15:54 17:54 19:54 21:55 23:55 time E [MJ]

Energy 1 small turbine (2014-Jul-1)

0,0 0,5 1,0 1,5 2,0 2,5

0:01 2:02 4:02 6:01 7:58 9:58 11:58 13:58 15:59 17:59 20:01 22:01 time E [MJ]

Energy 1 small turbine (2014-Oct-1)

0,00 0,02 0,04 0,06 0,08 0,10

0:01 1:55 3:55 5:53 7:50 9:46 11:45 13:45 15:49 17:45 19:44 21:42 23:36 time E [MJ]

 



 

day day day ith windt windt i windt,

T + ith Δt, N t P = E

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Produced energy

• During the period of the project the wind

speed, the pressure of air, the temperature of air and the sunlight is monitored in every Dt=5 minutes automatically by a local weather station, so it is available for us.

• The total daily production of electrical energy

in our hybrid system on ith day can be determined by knowing, separately, the daily energy production of the solar modules and the daily energy production of the wind turbines:

, E + E = E

i windt i photov i ee , , ,

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Accumulators

• When electrical energy is generated in solar

modules and/or in wind turbines it is stored instantly in accumulators according to the model assumption.

• I would like to discuss what size of

accumulator capacity (Eacc_max) is suitable for the parameters given in our off-grid system.

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• 4. Energy input and output and energy storage
• In order to determine the necessary storage

capacity of batteries, we study the energy inputs (produced energy) and outputs (dissipated energy) of the system in details.

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Heat transmission

• The rate of heat transmission (transfer) is directly

proportional to the temperature difference between the surroundings and the body.

• The heat transmission power from the environment to

the building through the walls (and roof) can be estimated by the expression [4]:

       ,

t T t T A U = t P = P

in

• ut

f heattr heattr

  

28

Heat radiation

• We tried to construct only an approximate

model accounting for thermal radiation.

• Heat transfer power from the environment to

the building due to thermal radiation can be estimated by the expression [5]:

     

 ,

t T t T A σ ε = t P = P

4 in 4

• ut

f rad rad

   

29

Heating of the house

• In this simple model our building is an off-grid

system and has electric heating; that is, electric current through a resistor releases heat.

• The electric heating power released is

proportional to the square of the current (Ic) and the resistance (R):

• The total electrical energy consumption of

resistance heating on ith day:

   .

t I R = t P = P

2 c heating heating



 

. T + ith Δt t P = E

day day day ith heating i heating





,

30

Cooling of the house

• The total electrical energy consumption of air

conditioner on ith day:

 





day day day ith aircond i cooling

T + ith Δt, t P = E

,

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Energy storage

• Internal energy
• Our building can store energy as internal

energy.

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Internal energy

• The internal energy of a macroscopic system

at a given temperature is proportional to its heat capacity.

, T T C T C = E

i

• ut

i in wall i in air ernal,i t in

2

, , ,

   

33

Accumulator system

• The energy Eacc(t) available in the

accumulators over time t can be neither negative nor can it surpass the storage capacity of the system:

 

, E t E

_max acc acc

 

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• 5. Energy balance

Heating season

• It is supposed for simplicity that in the ‘heating

season’ the internal energy of the model house on ith day:

. E + E + E η + E = E

i rad i heattr i heating heating 1 i ernal t in i ernal t in , , , , ,





35

Energy stored in accumulators

• In the ‘heating season’ the energy stored in

accumulators at the end of ith day:

. E E E + E + E = E

i eapp i heating i windt i photov 1 i acc i acc , , , , , ,

 



36

Non heating season

• In the ‘non heating season’ the internal energy
• f model house on ith day:

. E + E + E C E = E

i rad i heattr i cooling cooling 1 i ernal t in i ernal t in , , , , ,

 



37

Energy stored in accumulators

• In the ‘non heating season’ the energy stored

in accumulators at the end of ith day:

. E E E + E + E = E

i eapp i cooling i windt i photov 1 i acc i acc , , , , , ,

 



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• 6. Simulations
• In the simulations we ‘estimated’ the energy

consumption of a typical house with 4 inhabitants.

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Produced energy

• In figure 7 the electrical energy produced by

photovoltaic modules and wind turbines can be seen in the 2 years period of project.

Produced energy

0,00 50,00 100,00 150,00 200,00 250,00 300,00 350,00 400,00 450,00 500,00 550,00 600,00 650,00 700,00

2012.10.01 2012.11.01 2012.12.01 2013.01.01 2013.02.01 2013.03.01 2013.04.01 2013.05.01 2013.06.01 2013.07.01 2013.08.01 2013.09.01 2013.10.01 2013.11.01 2013.12.01 2014.01.01 2014.02.01 2014.03.01 2014.04.01 2014.05.01 2014.06.01 2014.07.01 2014.08.01 2014.09.01 2014.10.01

Days

Energy [MJ] E_pv_modules [MJ] E_wind_turbines [MJ]

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Energy consumption

• In figure 8 the electrical energy consumption
• f the house (electrical home appliances,

electric heater and air conditioner) is shown in the 2 year period of the project.

Energy consumption

0,00 50,00 100,00 150,00 200,00 250,00 300,00 350,00 400,00 450,00 500,00 550,00 600,00 650,00 700,00

2012.10.01 2012.11.01 2012.12.01 2013.01.01 2013.02.01 2013.03.01 2013.04.01 2013.05.01 2013.06.01 2013.07.01 2013.08.01 2013.09.01 2013.10.01 2013.11.01 2013.12.01 2014.01.01 2014.02.01 2014.03.01 2014.04.01 2014.05.01 2014.06.01 2014.07.01 2014.08.01 2014.09.01 2014.10.01

Days Energy [MJ]

E_electric_appliances [MJ] E_electric_heater [MJ] E_air_conditioner [MJ]

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Capacity of the accumulator system

• Computer simulation is performed in order

to determine the necessary capacity of the storage unit [6].

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With electric heating

• In the simulation with the given data the

necessary capacity of the energy storage unit that must be chosen is approx. 45097 MJ, in

• rder to prevent blackouts every day in the 2

year period of the project.

• In figure 9 the electrical energy of accumulator

system is shown.

E_acc_with_electric_heating [MJ]

10000 20000 30000 40000 50000

2012.10.01 2012.12.01 2013.02.01 2013.04.01 2013.06.01 2013.08.01 2013.10.01 2013.12.01 2014.02.01 2014.04.01 2014.06.01 2014.08.01 2014.10.01

Days

E_acc [MJ]

43

• The capacity of the accumulator-system

derived from the simulation has a value too large for a real-world storage system.

• It can not be realised in the real world in a

house.

44

Without electric heating

• If the electric heating is rejected and fossil fuel

(e.g. wood) heating is applied, then the necessary capacity of storage unit is approx. 547.5 MJ, according to our simulation. In figure 10 the electrical energy of accumulator system can be seen (without electric heating).

E_acc_without_electric_heating [MJ]

100 200 300 400 500 600

2012.10.01 2012.12.01 2013.02.01 2013.04.01 2013.06.01 2013.08.01 2013.10.01 2013.12.01 2014.02.01 2014.04.01 2014.06.01 2014.08.01 2014.10.01

Days

E_acc [MJ]

45

• That storage capacity might be realised, but it

would be very expensive: e.g. an automotive battery is usually lead-acid type, and is made

• f galvanic cells in series to provide 12 V.
• The electrical energy stored in a common

automotive accumulator is about 2.5 MJ, that is, 219 pieces of similar car battery could store 547.5 MJ electrical energy, theoretically.

46

• 7. Conclusion
• One of the goals of this project was to strengthen
• ur students’ internal motivation for learning

about the topic of renewables.

• The modern topics of physics can help in raising

the interest of the students and motivating them to learn the subject.

47

• A simple mathematical description of the energy

flow of a house with off-grid power generating system was given.

48

Theory and practice

• We think that this student project helps to

strengthen connection between theory and practice, improving practice within the field of physics education.

49

References

• [1] Renewable Energy Policy Network for the 21st Century,

Renewables 2013: Global Status Report

• http://www.ren21.net/Portals/0/documents/Resources/GSR/2

013/GSR2013_lowres.pdf

• [2] Blasone M, Dell’Anno F, De Luca R and Torre G 2013 A

simple mathematical description of an off-grid hybrid solar– wind power generating system Eur. J. Phys. 34 763-71.

• [3] De Luca R and Desideri P 2013 Wind energy: an

application of Bernoulli’s theorem generalized to isentropic flow of ideal gases Eur. J. Phys. 34 189–97.

• [4] Budo A 1997 Experimental Physics I, Nemzeti TK,

Budapest.

• [5] Budo A 1997 Experimental Physics III, Nemzeti TK,

Budapest.

• [6] Beke T 2015 A nap- és a szélenergia lakossági

felhasználási lehetőségeinek modellezése iskolai

• projektfeladatban. Fizikai Szemle, 65 (7-8) 263–269.

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Acknowledgements

• This lecture has been presented as part of

Physics Education PhD program at Eötvös University (ELTE, Hungary), Faculty of Science, Institute of Physics.

• I would like thank Prof. Dr Tamás Tél (the

head of the program) and Dr Gyula Bene (the supervisor), who helped me with useful information and data.

• I would like to thank my colleague Antal

Fekete and our students for their contribution to the project.