MBA Renewables Module 1, Renewable Energy and Energy Efficiency Systems and Concepts

Written Assignment of Group 6

Zero Energy Home

By

(alphabetical)

Riikka Lauhkonen-Seitz Mario Maras

Mattias Sääksjärvi Adriana Stefanac

18 January 2013

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Table of contents 1. Introduction .................................................................................................................................................................... 2

2. Description of the home ................................................................................................................................................. 2

2.1. House facts .............................................................................................................................................................. 2

2.2. Relevant ambient conditions ................................................................................................................................... 2

2.3. Energy consumption ............................................................................................................................................... 3

2.3.1. Space heating Qroom ......................................................................................................................................... 3

2.3.2. Water heating QH2O ......................................................................................................................................... 4

2.3.3. Electrical energy Wel ....................................................................................................................................... 4

3. Results ............................................................................................................................................................................ 5

3.1. Solar Water Heater ................................................................................................................................................. 5

3.2. Wood boiler ............................................................................................................................................................ 6

3.3. Micro Wind Turbine ............................................................................................................................................... 8

3.4. Photovoltaic .......................................................................................................................................................... 10

3.5. REN fractions of the proposed renewable technology concept ............................................................................ 12

4. Discussion and Recommendation ................................................................................................................................ 13

4.1. Heat ....................................................................................................................................................................... 13

4.2. Electricity .............................................................................................................................................................. 13

Sources ............................................................................................................................................................................. 15

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1. Introduction The objective of this report is to provide a reasonable site-specific technical concept of sustainable domestic energy supply for the chosen conventional grid-connected home consisting of several renewable energy technologies which combined meet the present energy consumption. 2. Description of the home 2.1. House facts Location: Outskirts of the city Eskilstuna, in the county of Södermanland, Sweden Property name: Lindholm, Grindstugan Origins: 18th century, rebuilt approx. early 20th century Material: Stone house, moderately isolated, windows with 2 glass panes Size: One level house, with a non-isolated attic, approximately 80 m² (excluding attic), 4 rooms,

kitchen, bathroom Energy system today: Total energy consumed is provided with electricity from the grid Water resources: Communal water pipes Occupation: Two-person household, occupied throughout the year 2.2. Relevant ambient conditions

Latitude: +59.37 (59°22'12"N) Longitude: +16.51 (16°30'36"E) Meteorological data: Eskilstuna is located in the south-east part of Sweden near Stockholm with lowest

temperatures of -2,95º C in average during winter, and highest temperatures of 16,5º C in average in the summer months. There are plenty of sun hours during summer time, however in winter the amount of sun is reduced to a few hours in the middle of the day. On the contrary average wind speeds are highest during winter and reach 5,22 m/s, and lowest in summer when they reach 4,39 m/s in average. (See Figure below).

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Eskilstuna, Sweden - Solar energy and surface meteorology (Gaisma, 2012). Surroundings: The house location is best described by the roughness length (z0 is 0,1m) as agricultural

land with some houses and 8 meter tall sheltering hedgerows with distance of approx. 500 meters. There are no feasible water resources, such as a lake or a river, close to the house nor usable raw material for biogas production.

2.3. Energy consumption Total annual energy consumption of the house is 18.000 kWh. Since the shares of space heating Qroom, water heating QH2O and electrical energy Wel of the total energy consumed are unknown, these are estimated using the given formulas as described in the next subchapters. 2.3.1. Space heating Qroom

In Eskilstuna, with monthly average temperatures Tair < 15°C space heating will be necessary most of the year, excluding summer months June-August (Figure 2).

Month Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec Tair, °C -3,32 -3,20 0,25 5,00 11,07 15,22 17,75 16,63 11,71 6,72 1,23 -2,34

Figure 2. Average monthly temperatures, Eskilstuna, Sweden (Gaisma, 2012). The formula to estimate the share of space heating Qroom of the total energy consumption is: !!""# = 1,2!"ℎ ∗ 15!! − !!"# / !! per m2 and month

Monthly and annual energy demand Qroom: Month Tair Qroom (kWh / m2) Qroom (kWh / 80 m2)

Jan -3,32 21,98 1.758,72

Feb -3,20 21,84 1.747,20

Mar 0,25 17,70 1.416,00

Apr 5,00 12,00 960,00

May 11,07 4,72 377,28

June n/a n/a n/a

July n/a n/a n/a

Aug n/a n/a n/a

Sept 11,71 3,95 315,84

Oct 6,72 9,94 794,88

Nov 1,23 16,52 1.321,92

Dec -2,34 20,81 1.664,64

Annually n/a 129,46 10.356,48

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2.3.2. Water heating QH2O Assumptions: consumption 40 liters at 60°C per person per day, mains cold water temperature 8°C The formula to estimate the share of warm water heating QH2O of the total energy consumption is: Q = V * ρ * c * ΔT Q = daily energy demand in kWh V = volume of water in m3 ρ = density of water = 1.000 kg / m3 c = specific heat capacity = 1,16 Wh / kgK Δ T = temperature difference between cold and hot water = 60°C – 8°C = 52°C Daily consumption of water (V) is: = 2 * 40 / 1.000 = 0,08 m3

Daily energy demand for hot water QH2O, day (kWh) thus is: = (0,08 * 1.000 * 1,16 * 52) = 4,8256 kWh

Monthly and annual energy demand for hot water QH2O, month & year:

Month # days QH2O, day (kWh) QH2O, month (kWh)

Jan 31 4,8256 149,59

Feb 28 4,8256 135,12

Mar 31 4,8256 149,59

Apr 30 4,8256 144,77

May 31 4,8256 149,59

Jun 30 4,8256 144,77

Jul 31 4,8256 149,59

Aug 31 4,8256 149,59

Sept 30 4,8256 144,77

Oct 31 4,8256 149,59

Nov 30 4,8256 144,77

Dec 31 4,8256 149,59

Annually 365 4,8256 1.761,34 2.3.3. Electrical energy Wel To calculate the annual electrical energy demand, the energy needed for space and water heating estimated in Chapters 2.3.1. and 2.3.2. is deducted from the total energy consumption. !!",!"#$!18.000  kWh  –  10.356,48  kWh   −  1.761,34  kWh   =  5.882,18  kWh    Based on the annual result, the average monthly electricity demand is !!",!"#$! = 490,18!"ℎ

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3. Results With no feasible water resources nor usable raw material for biogas production nearby Micro Hydro Power Plant and Biodigester are left out as possible solutions. Relevant data was therefore calculated for the remaining technologies which use sources available at the location (sun, wind and wood biomass). The results of the calculations show that using these technologies at the particular location is justified to meet the energy demand. We recommend a hybrid solution of the four renewable energies analysed in the next Chapters. Space heating and energy required for domestic hot water will be produced with a Wood-Pellet Boiler and Solar-Thermal Hybrid. The demand for electrical energy will be produced with a combination of Photovoltaic modules and a Micro Wind Turbine. 3.1. Solar Water Heater Q1. How much is the monthly and annual heat demand for warm water? See Chapter 2.3.2., water heating QH2O. Q2. How much is the monthly and annual global solar radiation energy? Data for insolation (measure of solar radiation energy received on a given surface area and recorded during a given time) for particular location per day can be retrieved from www.gaisma.com. Therefore, monthly and annual radiation data are easily calculated.

Month Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec 0,34 1,02 2,24 3,77 5,15 5,30 5,12 4,07 2,64 1,24 0,57 0,20 10,54 28,56 69,44 113,10 159,65 159,00 158,72 126,17 79,2 38,44 17,10 6,20

2

,, /12,966 mkWhIIDec

Janmonthmonthsolyearsol ∑

=

==

Q3. What is theoretically the optimum collector position (azimuth, inclination) at the selected location? What should be considered e.g. during winter? The house is located in the northern hemisphere and therefore the collector should be directed to south. The azimuth of the module is an angle between module direction and south and is noted as (α). Inclination of the module is defined as (β) and equals latitude minus 10!. Azimuth (α) = 90! −  Longitude, !"#$""% Azimuth (α) = 100 −  Longitude, !"# Inclination (β) = Latitude - 10!, !"#$""% Inclination (β) = Latitude – 11,11, !"# Latitude = 59!22′12′′= 59,37 degrees = 69,97 grd Longitude = 16!30′36′′= 16,51 degrees = 18,34 grd

1  !"# =  1  !"#$""

0,9

α = 100 – 18,34 = 81,66 grd β = 69,97 – 11,11 = 58,86 grd As to the second question regarding wintertime, because we have a horizontally aligned collector of β=0° given in the Assumptions/Simplifications we should consider the fact that, depending on the amount of snow, the collector might fall under snow and get frost on the panels. There is special equipment to melt the snow and ice on the collector’s surface, e.g. solar-power heating strips, but their ability to melt the snow does of course vary depending on the amount of snow and outside temperature.

Isol,day kWh /m2day!" #$

Isol,month kWh /m2month!" #$

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Q4. What is the collector area of the proposed solution? Our proposition is to use the solar water heater from April to October. These seven months can be considered “snow-free” months in the region. The heavy burden of snow, low temperatures and frost that sets on the solar panels during the winter months might cause too much problems to make up for the small amount of possible energy production during the dark months in Sweden. For calculating the collector area we use the following formula:

!"##$!%"&  !"#! =!"#$!%#  !"#$%  !"#$%&'()"#   ∙  !"#$%"!  !"#$%  !"#$%&'(!"#$!%#  !"#$%  !"#$%  !"!"#$"%$&'   ∙  !"!#$%  !""#$#!%$&

Daily energy demand for hot water QH2O is 4,8256 kWh (see Chapter 2.3.2). Desired solar fraction: 110 % The desired solar fraction is set so that we have extra solar resources for spring and autumn when solar irradiation is not optimal for our usage. For calculating the daily solar irradiation we use the daily average of the solar irradiation between April and October:

Month Apr May Jun Jul Aug Sept Oct Total

3,77 5,15 5,30 5,12 4,07 2,64 1,24 27,29

Source: Gaisma 2012 !",!"  !"!/!!

!  !"#$!!= 3,90   !"ℎ !! per day on average for the period.

η = 50% Collector area = 2,72 m2 The collector area is rounded to 3,0 m2. For this purpose our solution is to use a double energy water-heater with 2 x 1,5m² panels named Solar Pro Inox 200 lt of the Greek company EcoPowerMarket (EcoPowerMarket, 2013). For the period April to October the total solar radiation energy is 834,28 kWh/m² (see Chapter 3.1., Q2). With an efficiency of 50% and a collector size of 3 m² this means a total solar yield of 1.251,42 kWh for the period: = Monthly solar radiation kWh * efficiency 50% * collector size 3m2

Month Apr May Jun Jul Aug Sept Oct Total

Solar yield [kWh] 169,65 239,47 238,50 238,08 189,26 118,80 57,66 1.251,42

Q5. What is the monthly and annual solar fraction of the proposed solution? See Chapter 3.5. 3.2. Wood boiler As discussed in Chapter 2.3., space heating will be necessary in our selected location most of the year, excluding summer months. Using electricity for space heating is often inefficient and uneconomical which is why we suggest assessing the possibility of wood pellet heating. Q1. How much is the monthly and annual heat demand for space heating? See Chapter 2.3., energy consumption. Q2. How much is the monthly and annual heat demand for water heating? See Chapter 2.3., energy consumption.

Isol,day kWh /m2day!" #$

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Q3. Which type of wood will be used and in which condition?

For the analysis we use wood pellets produced according to the new European pellet standard EN 14961-2 “Solid biofuels – Fuel Specifications and Classes – Part 2: Wood pellets for non-industrial use”, property class A1 (Alakangas, 2010: 5, 12). Most Swedish pellet producers are now using the European standard instead of the old Swedish national standard (Mörner, 2011: 10).

Q4. What is the water content of the wood?

Water content of the pellets used is w ≤ 10% (Alakangas, 2010: 12).

Q5. What is the lower heating value (LHV) of fresh matter (FM) of the wood?

Lower heating value of fresh matter of the pellets used is LHVFM ≥ 16,5 MJ/kg (Alakangas, 2010: 12). The corresponding heating value in kWh is 4,60 kWh/kg:

3,6 MJ = 1 kWh à 16,5 MJ/kg = 4,60 kWh/kg (=16,5 MJ / 3,6 MJ) Q6. How much is the monthly and annual consumption of wood? The energy demand for space heating Qroom was calculated in Chapter 2.3.1. In order to define the share of water heating demand that is to be covered by the pellet boiler, the energy produced by the solar water heater (SWH) (see Chapter 3.1) has to be deducted from the total water heating demand QH2O:

Month QH2O (kWh) Energy produced by SWH (kWh)

Remaining energy demand to be produced with pellets (kWh)

Jan 149,59 0,00 149,59

Feb 135,12 0,00 135,12

Mar 149,59 0,00 149,59

Apr 144,77 169,65 0,00

May 149,59 239,47 0,00

Jun 144,77 238,50 0,00

Jul 149,59 238,08 0,00

Aug 149,59 189,26 0,00

Sept 144,77 118,80 25,97

Oct 149,59 57,66 91,93

Nov 144,77 0,00 144,77

Dec 149,59 0,00 149,59

Annually 1.761,34 1.251,42 846,57 Thus, the monthly and annual consumption of pellets (!!") for space heating (Qroom) and water heating (QH2O) using a boiler with an efficiency of 90% is:

Month Qroom (kWh) QH2O (kWh) LHW (kWh/kg) Efficiency ηth (%) Consumption mFM (kg) Consumption mFM (t)

Jan 1.758,72 149,59 4,6 90% 373,37 0,37

Feb 1.747,20 135,12 4,6 90% 368,28 0,37

Mar 1.416,00 149,59 4,6 90% 306,31 0,31

Apr 960,00 0,00 4,6 90% 187,83 0,19

May 377,28 0,00 4,6 90% 73,82 0,07

Jun 0,00 0,00 4,6 90% 0,00 0,00

Jul 0,00 0,00 4,6 90% 0,00 0,00

Aug 0,00 0,00 4,6 90% 0,00 0,00

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Sept 315,84 25,97 4,6 90% 66,88 0,07

Oct 794,88 91,93 4,6 90% 173,51 0,17

Nov 1.321,92 144,77 4,6 90% 286,96 0,29

Dec 1.664,64 149,59 4,6 90% 354,96 0,35

Annually 10.356,48 846,57 4,6 90% 2.191,90 2,19 Q7. How much is the required wood storage volume per season? The bulk density of the pellets is 600,00 kg/m3 (Alakangas, 2010: 12). With annual consumption of 2.191,90 kg the required annual storage volume is:

!store =  2.191,90  !"600,00  !"/!3 = !,!"  !3

Q8. What is the monthly and annual heat fraction of the proposed solution? See Chapter 3.5. 3.3. Micro Wind Turbine Q1. What is the monthly and annual average wind speed at indicated height? The monthly average wind speed for the particular location is to be found at Gaisma (See: http://www.gaisma.com/en/location/eskilstuna.html). In the help section of the web site the indicated height is given – it reads that wind speed values are for 50 meters above the surface of the earth (See: http://www.gaisma.com/en/info/help.html).

Month Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec v wind, 50 [m/s] 5,42 4,95 5,00 4,84 4,73 4,52 4,37 4,28 4,86 5,14 5,29 5,29

Based on monthly average wind speed data the annual average wind speed at indicated height is calculated as follows

!!"#$,!",!"#$ = !!"#$,!"

!"#

!"#$!!!"#

12 = 4,89  !/!

Q2. How much is the approximate roughness length at the selected location? According to the input by the house owner the roughness length at the chosen location is Z0 = 0,1 m, meaning that the house is built on agricultural land with some houses and 8 meter tall sheltering hedgerows with a distance of approximately 500 meters and that the distance above ground level where the wind speed should theoretically be zero is 0,1 m. Q3. How much is the monthly and annual average wind speed at 10m? The monthly and annual average wind speed at hub height of the rotor (given in the Assumptions / Simplifications) can be calculated by using the logarithmic profile with !! = 0,1! ℎ! = 50! ℎ! = 10! !!  is wind speed at ℎ! !!  is  wind  speed  at  ℎ! !! = !!"#$,!"

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Month Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec v wind, 10 [m/s] 4,02 3,67 3,71 3,59 3,51 3,35 3,24 3,17 3,60 3,81 3,92 3,92

Based on monthly average wind speed data the annual average wind speed at 10m height is calculated as follows:

!!"#$,!",!"#$ = !!"#$,!",!"#$!

!"#

!"#$!!!"#

12 = 3,62  !/!

Q4. What is the swept area (or rotor diameter) of the proposed wind turbine?

In order to meet the electricity demand of the house given in Chapter 2.3.3., the theoretically optimal swept area of the wind turbine is calculated as follows:

Efficiency = Useful Output Energy / Input Energy

Useful Output Energy = Input Energy * Efficiency

Input Energy = Power Input * Time

Useful Output Energy = Power Input * Time * Efficiency

Power Input – ! =   !! ∗ ρ ∗ A ∗ !!

!!"#$,!"#$ =!!∗ ρ ∗ A ∗ !! ∗ ! ∗ η

! =2 ∗!wind,  year

ρ ∗ !! ∗ ! ∗ η

!!"#$,!"#$ = 5.882,18  !"ℎ (Annual electricity demand)

ρ!"# = 1,2!"/!! = const. (independent of temperature)

!!"#$,!",!"#$ = 3,62  !/!

t = 8760h

η wind = c p η other = 30% = const., including aerodynamic, mechanical and electrical losses (independent of wind speed, rotor diameter, tip speed ratio etc.).

The theoretically necessary swept area is therefore:

A = 78,64 m2

The respective rotor diameter is:

!!"#"! =!!∗ !!"#"!

!∗ π

!!"#"! = 10  !

It was not possible to find a small scale turbine for residential use with such rotor diameter. Therefore we propose to use the 10 kW BWC Excel 10 with a rotor diameter of 7 m (Bergey, 2012).

The swept area of the proposed wind turbine is 38,47 m2.

Q5. How much is the monthly and annual energy generation of the proposed solution?

Useful Output Energy = Power Input * Time * Efficiency

Therefore,

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!!"#$,!"#$! =!!∗ ρ ∗ !!"#"! ∗ !3 ∗ ! ∗ η!"#$

Month Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec W wind, month [kWh]

333,78 229,65 262,04 230,02 221,84 187,34 174,95 164,36 232,88 284,68 300,32 310,33

!!"#$,!"#$ = !!"#$,!"#$!

!"#

!"#$!!!"#

!!"#$,!"#$ = 2.932,21  !"ℎ (electricity produced by wind turbine)

Q6. What is the monthly and annual REN fraction of the proposed solution? See Chapter 3.5.

Q7. If you have the annual distribution of wind speed, take these figures and ignore the monthly values.

For the chosen location data on annual distribution of wind speed is not available, only monthly average wind speed.

Q8. What is the main error in calculating the wind power based on average wind speed?

The importance of accurate wind speed becomes clear when we take into account how the speed affects the power. Due to the fact that the Power of the Wind is proportional to the wind speed cubed, even a small change in wind speed influences the wind power very much. Hence it is important to know the wind speed distribution precisely (fewer hours with faster winds will still produce more power), and not just the average wind speeds, because any error is magnified when calculating the power. Furthermore, in our assignment we calculated the average wind speeds at hub height of the rotor at the location by using only the roughness length, which was estimated (not derived from measurements), and not by performing wind measurements for the site. According to the learning materials this approximation is only a good guess. Hence using the average wind speeds calculated based on the estimated roughness length to calculate the Power of the Wind can also be merely an approximation. 3.4. Photovoltaic Q1. How much is the monthly and annual global solar radiation energy? See Chapter 3.1., Solar Water Heater Q2. How much is the monthly and annual global solar radiation energy? Q2. How much is the monthly and annual power generation per m2 module? Monocrystalline module DM205-M125-72 manufactured by the Chinese company DMEGC is proposed with an efficiency of !module = 14,1% (see DMEGC Solar Energy, 2012), which is similar to the efficiency given in the Assumptions/Simplifications. Efficiency is the ratio of output energy and input energy. In terms of module efficiency, input energy per m2 is irradiation coming from the sun and output energy per m2 is electrical energy produced by PV module.

PV module produces DC current, therefore an inverter is needed. Efficiency of the inverter is ratio of AC electrical energy and DC electrical energy produced by the PV module. In this assignment !inverter = 90%.

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   Therefore electrical energy produced per m2 is as follows:

Month Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec WPV, AC, m2 [kWh/m2] 1,34 3,62 8,81 14,35 20,26 20,18 20,14 16,01 10,05 4,88 2,17 0,79

 

22,,,2,,, /60,122 mkWhWW

Dec

JanmonthmmonthACPVmyearACPV ∑

=

==  

In order to get electrical energy produced per module, we have to multiply the monthly results with the surface area of the proposed module Am, which is 1,28 m2 (DMEGC Solar Energy, 2012).

Month Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec

WPV, AC, module [kWh] 1,71 4,64 11,28 18,37 25,93 25,83 25,78 20,49 12,86 6,24 2,78 1,01

kWhWWDec

JanmonthulemonthACPVuleyearACPV ∑

=

== 93,156mod,,,mod,,,

Q3. What is theoretically the optimum module position (azimuth, inclination) at the selected location? See Chapter 3.1., Solar Water Heater Q3. What is theoretically the optimum collector position (azimuth, inclination) at the selected location? Q4. What is the PV module area of the proposed solution? The rest of the electrical energy demand, which cannot be produced by the Micro Wind Turbine and has therefore to be covered by the PV plant is as follows WPV,year = Wel,year – Wwind,year = 5.882,12 kWh – 2.932,21 kWh = 2.949,97 kWh The module area needed to provide this amount of energy is therefore APV = WPV,year / WPV,AC,year,m2 = 2.949,97 kWh / 122,60 kWh/m2 = 24,06 m2 The necessary number of modules is therefore APV/Am = 18,80 Hence to meet the rest of the electrical energy demand 19 modules will be necessary, so the PV module area of the proposed solution is APV,19 = Am * 19 = 24,32 m2 With these modules the monthly and annual energy generation is as follows

Month Jan Feb Mar Apr May Jun Jul Aug Sept Oct Nov Dec !!",!",!"#$! 32,53 88,14 214,31 349,05 492,71 490,71 489,84 389,39 244,43 118,65 52,77 19,13

kWhWWDec

JanmonthmonthACPVyearACPV 65,981.2,,,, ∑

=

==

Q5. What is the monthly and annual solar fraction of the proposed solution? See Chapter 3.5.

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3.5. REN fractions of the proposed renewable technology concept The monthly and annual energy consumption of the house is summarized in the below table:

Month Space heat Qroom (kWh) Water heat QH2O (kWh) Electricity Wel (kWh)* Total (kWh)

Jan 1.758,72 149,59 490,18 2.398,49

Feb 1.747,20 135,12 490,18 2.372,50

Mar 1.416,00 149,59 490,18 2.055,77

Apr 960,00 144,77 490,18 1.594,95

May 377,28 149,59 490,18 1.017,05

Jun 0,00 144,77 490,18 634,95

Jul 0,00 149,59 490,18 639,77

Aug 0,00 149,59 490,18 639,77

Sept 315,84 144,77 490,18 950,79

Oct 794,88 149,59 490,18 1.434,65

Nov 1.321,92 144,77 490,18 1.956,87

Dec 1.664,64 149,59 490,18 2.304,41

Annually 10.356,48 1.761,34 5.882,18 18.000,00 * monthly average The monthly and annual energy produced by the proposed renewable technologies were calculated in Chapters 3.1.-3.4. and are summarized below:

Month PV (kWh) Wind turbine (kWh) SWH (kWh) Wood boiler (kWh) Total (kWh)

Jan 32,53 333,78 0,00 1.908,31 2.274,62

Feb 88,14 229,65 0,00 1.882,32 2.200,11

Mar 214,31 262,04 0,00 1.565,59 2.041,94

Apr 349,05 230,02 169,65 960,00 1.708,72

May 492,71 221,84 239,48 377,28 1.331,31

Jun 490,71 187,34 238,50 0,00 916,55

Jul 489,84 174,95 238,08 0,00 902,87

Aug 389,39 164,36 189,26 0,00 743,00

Sept 244,43 232,88 118,80 341,81 937,92

Oct 118,63 284,68 57,66 886,81 1.347,78

Nov 52,77 300,32 0,00 1.466,69 1.819,79

Dec 19,13 310,33 0,00 1.814,23 2.143,70

Annually 2.981,65 2.932,21 1.251,42 11.203,05 18.368,32 Therefore, the monthly and annual REN fractions of the proposed technologies of total energy consumption are: Month Solar fraction fPV (%) Wind fraction fWIND (%) SWH fraction fSWH (%) Heat fraction fwood (%) Total fREN (%)

Jan 1,36% 13,92% 0,00% 79,56% 94,84%

Feb 3,72% 9,68% 0,00% 79,34% 92,73%

Mar 10,42% 12,75% 0,00% 76,16% 99,33%

Apr 21,88% 14,42% 10,64% 60,19% 107,13%

May 48,45% 21,81% 23,55% 37,10% 130,90%

Jun 77,28% 29,51% 37,56% 0,00% 144,35%

Jul 72,79% 27,35% 37,21% 0,00% 141,12%

13    

Aug 60,86% 25,69% 29,58% 0,00% 116,13%

Sept 25,71% 24,49% 12,49% 35,95% 98,65%

Oct 8,27% 19,84% 4,02% 61,81% 93,94%

Nov 2,70% 15,35% 0,00% 74,95% 92,99%

Dec 0,83% 13,47% 0,00% 78,73% 93,03%

Annually 16,56% 16,29% 6,95% 62,24% 102,05% The four REN technologies together produce 102,05% of the total annual energy demand. Energy surplus is therefore minimized to the best possible extent. 4. Discussion and Recommendation 4.1. Heat The task was to find a renewable solution for domestic hot water supply and space heating. In northern hemisphere the amount of sunlight fluctuates drastically between summer and winter. While the sun is up even during night time in summer, the amount of sun during winter goes below 6 hours a day. The average temperature difference between July and December is around 21°C. Therefore our recommendation for domestic hot water supply is a hybrid solution using a solar water heater during the period between April and October and a wood pellet boiler during rest of the year or when solar collectors cannot provide enough heat to meet the hot water demand. For space heating we suggest using wood pellet boiler throughout the year. Hybrid heating systems combining pellet and solar water heating have become more common and are particularly suitable for small houses or summer houses. A solar water heater can be an easy and environmentally friendly way of turning sun’s energy into water heat for a normal household. They are considered easy to install and hold a low maintenance cost after installation. The problem with a solar water heater in cold climates is winter time. With a horizontal alignment of 0° as given in the assumptions, snow and frost combined with cold temperatures can reduce the energy produced. Furthermore, with only little sunlight during winter the system might also lead to a shortage of hot water during the coldest months. However, due to its cost efficiency (especially on sunny days during June and July) the solar water heater is a good option to use in a hybrid system combined with a wood boiler. Sweden has long traditions in wood pellet production and is one of the leading countries globally in terms of wood pellet consumption. Although the most common source for heating still is electricity, the potential for biomass heating is considered notable due to high electricity prices (Mörner, 2011: 4). Domestic raw material is available thanks to Sweden’s notable wood processing industry which provides residues for pellet production, e.g. sawdust. Pellet stoves are relatively easy to operate as normally they only require loading of pellets and igniting the flame. Pellet stoves however need regular maintenance, e.g. emptying of ashes weekly or monthly, to keep them performing well. Given the Assignment specifications, the alternative for a solar water heater would be to use only wood pellets or electricity. Due to the efficiency of a solar water heater during summer months, we do however find a hybrid solution the best possible. As regards alternatives for wood boiler, the only alternative would be to use electricity for space heating as well (solar thermal systems that can be used for space heating exist but these were not part of the Assignment). However, as space heating constitutes the largest part of total energy consumption (in our house 57%), it is not feasible to use electricity produced using either wind or sun to meet the vast demand for space heating. The amount of energy produced by the chosen wind turbine is the highest that can be achieved when using wind as a resource at the particular location (see following Chapter 4.2., Electricity), and it is not nearly enough to meet the space heating demand, especially not in winter. As regards PV, with the solar radiation on site, this technology is even less capable of meeting the demand for space heating since it generates the least amount of energy when demand is highest. For these reasons a hybrid system combining pellet heating and solar water collector is an ideal solution for our house. 4.2. Electricity Since no water resources nor usable raw material for biogas production are available in the selected region, a Micro Hydro Power Plant and a Biodigester had to be excluded which leaves wind and sun as possible resources for electrical energy production.

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Sweden is located in the northern hemisphere with significantly smaller amount of annual solar radiation in comparison to southern hemisphere countries. Therefore wind seemed as the more logical choice. The average annual wind speed for Eskilstuna at measured height lies at 4,89 m/s. Wind tends to blow faster in winter time and its average speed is below average during summer. However, the performed calculations indicate that the proposed Micro Wind Turbine BWC Excel 10kW (manufactured by the US based company Bergey WindPower Co., recommended for larger rural homes, farms and businesses with wind turbine noise less than prevailing background noise below 6m/s at hub height; the wind turbine also complies with the microgeneration certification scheme (MCS) which is the European standard for technologies used to produce electricity and heat from renewable sources) with the biggest rotor diameter that was possible to obtain for a smaller scale turbine cannot produce all of the necessary energy, not even with increased rotor hub height (in the Assumptions/Simplifications the hub height of the rotor is 10m). Therefore another technology needed to be considered. As regards sun as the other possible resource for electricity, solar radiation in Eskilstuna is much higher in summer than in winter when the amount of sun is reduced to a few hours in the middle of the day. The chosen PV modules with an efficiency of 14,1% (in accordance with the efficiency given in the Assumptions/Simplifications for for Photovoltaic Plant) are manufactured by the Chinese company DMEGC. These are Monocrystalline Silicon modules with the highest module efficiency compared to other technologies and, according to the manufacturer, capable of high performance under low light conditions (cloudy days, morning and evenings) which makes them very suitable for the particular location. If only PV would be used for electricity production, the area needed for the installation of the plant would double. The PV plant would produce a large surplus of energy in summer (compared to the average monthly electricity consumption of 490,18 kWh), and could not meet the monthly average during the winter months by far. The calculations performed show that, with more wind in winter and more sun in summer, the Micro Wind Turbine and Photovoltaic are the perfect match for the particular location in order to meet the present electricity demand.

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Sources Alakangas E. (2010). “New European Pellets Standards. European Pellets Conference. 3-4 March 2010, Wels. Updated 10 March.” Retrieved on 15 Dec 2012 from http://www.propellets.at/images/content/pdfs/alakangas_new_european_pellets_standards_10032010.pdf Bergey (2012). “BWC Excel 10kW” Retrieved on 6 Jan 2013 from http://bergey.com/products/wind-turbines/10kw-bergey-excel EcoPowerMarket (2012). “Double energy solar water-heater, SOLAR PRO INOX, 200 lt”. Retrieved on 16 Jan 2013 from http://www.ecopowermarket.gr/product_info.php?cPath=75_76&products_id=123 Gaisma (2012). Retrieved on 15 Dec 2012 from http://www.gaisma.com/en/location/eskilstuna.html Mörner H. (2011). „Sweden Pellet Report“. Svebio. PellCert Project. Retrieved on 1 Jan 2013 from http://www.enplus-pellets.eu/wp-content/uploads/2012/01/SE_pellet_report_Jan2012.pdf DMEGC Solar Energy (2012). “Monocrystalline module DM205-M125-72” Retrieved on 15 Dec 2012 from http://www.dmegcsolar.com/download/DM205-M125-72.pdf