IMPACT OF THE PV GENERATOR’S ORIENTATION ON THE ENERGETIC ASSESSMENT OF PV SELF-CONSUMPTION SYSTEMS CONSIDERING INDIVIDUAL RESIDENTIAL LOAD PROFILES Tjarko Tjaden ∙ Johannes Weniger ∙ Joseph Bergner ∙ Felix Schnorr ∙ Volker Quaschning
Reference PV self-consumption system and impacts on the energetic performance
Furthermore, the system technology and the models as well as the assumptions of the simulation are affecting the calculated results.
However, there could be non-negligible impacts of the individual seasonal and diurnal variations of the load and PV profile on the energetic assessment of those systems.
PV generator
Load profile
PV generation profile
= PV inverter
=
With the support of 74 representative measured domestic load profiles, this contribution shows up three characterization methods for the electric demand. Further on, basic relationships between PV system size and optimum orientation will be presented by various parameter variations. Finally, calculations for typical installed PV battery systems are conducted to highlight the sensitivity of all possible PV generator orientations on the energetic performance.
Battery
Yearly irradiation Generator’s azimuth angle Generator’s tilt angle Location Shading Future development
System technology
Yearly load demand Type of household Size of household Electric appliances User behavior Future development
Simulation
Rated PV power Battery capacity Battery power Charging method System topology
Time resolution Battery model PV model Inverter model Assumption for losses
= =
=
Charge regulator and inverter
Circuit breaker Loads
kWh
2.0
80% 90% 70%
1.5
1 Minute BSRN, DWD-Station Lindenberg, Germany used from VDI 4655 south-oriented, 35° tilt angle performance ratio 83%, AC-coupled lithium-ion-battery round-trip-efficiency 84% max. inverter power 1 kW/kWh
Battery storage:
Self-consumption rate and degree of self-sufficiency can be visualized by normalization the system size to the yearly load demand in MWh, see figures on the right-hand side.
60%
60%
50%
50% 1.0
40%
40%
30%
30%
0.5
20% 10%
20% 0.5
1.0
1.5
2.0
2.5
PV system size in kWp/MWh Degree of self-sufficiency
2.5
General conditions for the reference system:
70%
80%
Energy meter
Grid
100% 90%
0.0 0.0
888.888
Simulation step size: Weather data: Load profile: PV system:
=
Control unit
Usable battery capacity in kWh/MWh
The biggest impacts are caused by seasonal and diurnal variations of the load demand and the PV generation.
Usable battery capacity in kWh/MWh
For calculating the benefit of a PV system, reference results for the self-consumption rate and the degree of self-sufficiency have already been presented. Thereby the load demand, PV generator and battery size are also taken into account.
Self-consumption rate
2.5
AC DC BAT
Electricity from residential photovoltaic systems is already cheaper than the price of the electricity from the grid. Therefore PV systems with high shares of self-consumed energy are economical preferable.
ACDC MPPT
Motivation and Approach
0%
100% 80%
2.0
90% 80% 70%
70%
1.5
60% 50%
60%
1.0
40% 50%
30%
40%
0.5
20%
30%
10%
20% 10%
0.0 0.0
0.5
1.0
1.5
2.0
2.5
0%
PV system size in kWp/MWh
Characterization of load profiles
Influence on the optimum azimuth angle Optimum orientation with 1 kWh/MWh
24
90 2 kWp/MWh
Average
Average
Average
30
Summer fraction
Optimum orientation with 1 kWp/MWh
Night fraction
90 75
16
0 0
-90 25
35 45 55 25 35 45 55 25 35 45 55 Noon fraction in % Noon fraction in % Noon fraction in % Optimum azimuth angle in dependency of the noon fraction for 74 load profiles using a PV battery system with 1 kWh/MWh and different generator sizes. Low noon fractions result in stronger orientation to the west. Larger-sized PV systems amplify this sensitivity and concurrently shift the optimum azimuth even more to the west.
Optimal orientation regarding PV size
45
315
360
30
optimal azimuth more to the west optimal tilt more to higher angles
Self-sufficiency of measured load profiles 2σ
1σ
average
10
60
Optimum orientation with 1 kWp/MWh 60
75%
65% 55%
20
25%
10 -90
60
50
50 40 30
45
20 10 60
80
40
70
Tilt angle in °
70
60
70
50 65
40 30
60
20
55
10 0
-80 -60 -40 -20 0 20 40 Azimuth angle in °
60
80
-30
0 30 Azimuth in
60
90
Optimal orientation for 74 load profiles using a PV battery system with 1 kWp/MWh and different battery sizes. Larger-sized batteries result in higher optimal tilt angles and at the same time in a stronger azimuth orientation regarding the energetic PV yield optimum.
• Individual load profiles together with the orientation of the PV generator have a significant impact on the energetic assessment of PV self-consumption systems.
80 75
-60
Summary
Self-consumption rate in %
80
Degree of self-sufficiency in %
80
30
35%
Mean self-consumption rate for all 74 load profiles 90
40
45%
Mean degree of self-sufficiency and statistical abbreviation for three relevant PV self-consumption system sizes as a result of 74 load profiles. The mean degrees of self-sufficiency deviate less than 2% from the reference results which can be seen as an approval of their general validity.
Mean degree of self-sufficiency for all 74 load profiles 90 55
without Battery 1 kWh/MWh 2 kWh/MWh Average
50
Mean energetic performance for all load profiles with 1 kWp & 1 kWh per MWh
Tilt angle in °
Optimal orientation regarding battery size
min / max
0.5 & 0.5 1&1 2&2 kWp/MWh & kWh/MWh
90
Optimum orientation for 74 load profiles using a PV battery system with 1 kWh/MWh and different generator sizes. Larger-sized PV generator sizes result in lower optimal tilt angles and at the same time to a stronger azimuth orientation regarding the diurnal load demand.
-80 -60 -40 -20 0 20 40 Azimuth angle in °
Optimum tilt angle in dependency of the summer fraction for 74 load profiles using a PV battery system with 1 kWp/MWh and different battery sizes. High summer fractions result in lower tilt angles. Larger-sized battery systems don’t change that sensitivity but shift the perfect tilt angle to higher levels.
Tilt angle in
30 20
0
20 30 40 50 60 20 30 40 50 60 20 30 40 50 60 Summer fraction in % Summer fraction in % Summer fraction in %
85%
Degree of self-sufficieny
Tilt angle in
270
45
Reference results
0 30 Azimuth in
Average
0
Presumptions Low noon fractions: Low summer fractions:
40
-30
135 180 225 Day of the year
30 40 50 60 70 30 40 50 60 70 30 40 50 60 70 Noon fraction in % Summer fraction in % Night fraction in % Definition of three energetic fractions for the 74 electrical load profiles to characterize the load demand regarding seasonal und diurnal differences.
0.5 kWp/MWh 1 kWp/MWh 2 kWp/MWh Average
-60
Average
15
60
-90
90
25 20 15 10 5 0
Optimum orientation with 1 kWh/MWh
50
2 kWh/MWh
60
8
0
-30
1 kWh/MWh
12
4
-60
without battery Average
20
Tilt angle in
1 kWp/MWh
Hour of day
0.5 kWp/MWh
Frequency
Azimuth angle in
60
Noon fraction
Influence on optimum tilt angle
50
Regarding typical rooftops in Germany with all possible azimuth angles and tilt angles between 10° to 60° the average degree of self-sufficiency only varies between 55 and 50%. Due to the average noon fraction, which is below 50%, the optimal azimuth angle is shifted slightly to the west. The mean self-consumption rate is more sensitive to changes in the orientation. Furthermore, higher self-consumption rates result in lower degrees of self-sufficiency and therefore shouldn‘t be maximized by orientation optimization.
• The presented characterization methods for the individual load profiles (noon & summer fraction) result in a better understanding for differences in the optimal orientation. • In general, for achieving high degrees of self-sufficiency, larger-sized PV generators result in lower tilt angles and different azimuth angles, triggered by the noon fraction. • Despite of that, larger-sized battery systems result in higher tilt angles and an azimuth orientation concentrating on the energetic optimum of the PV yield. • Hence, the impact of the PV generator‘s orientation on the energetic assessment is lower than the influence of individual load profiles. • The presented reference results are still reliable for a first estimation of the energetic assessment of PV selfconsumption systems.
University of Applied Sciences (HTW) Berlin, Wilhelminenhofstraße 75A, 12459 Berlin, Germany ∙ Email:
[email protected] ∙ Web: http://pvspeicher.htw-berlin.de
