This document summarizes presentations given at an EPRI Fall Meeting on battery integration and power optimizers. It discusses E.ON's solar business and objectives to reduce costs. Applications and opportunities of battery integration with solar plants are overviewed, including a Puerto Rico example where batteries were required to meet ramp rate and frequency control standards. Optimization of solar projects both with and without batteries is covered. Testing results of power optimizers show performance enhancements in shading conditions but no overall benefit without shading. Future tests will focus on optimizing balance of system costs at large solar farms.

1. 1. Battery Integration with Solar Power Plants
2. Power Optimizer
Jake McKee, Head of engineering Solar PV
Stefan Christ, Manager R&D Solar
EPRI Fall Meeting, Atlanta, Sept 29th 2014

2. Agenda
Battery Integration with Solar Power Plants Jake McKee
Power Optimizer test results Stefan Christ
Q & A Stefan & Jake
2 EPRI Fall Meeting, Battery integration and Power Optimizer, Sep 29th, 2014

3. Introduction to E.ON’s PV business
E.ON‘s PV Business:
 ~80 MW of utility scale installations in Europe and in the U.S. plus 40 MW
currently under construction
 Rooftop PV business in Europe
E.ON‘s Objective is to make PV more attractive
 E.ON constantly strives to cut LCOE for its PV installations
 Different options like optimizing tracking as well as other advance concepts
 Power Optimizer (POs) explored to cut LCOE for utility scale and to
increase flexibility in residential systems
 Integrating batteries and PV to improve the value of PV power to energy
system, e.g. better control (reducing ramp rates), ancillary services.
3 EPRI Fall Meeting, Battery integration and Power Optimizer, Sep 29th, 2014

4.  Applications & Opportunities
 Optimization of Solar Projects without Batteries
 Experiences with Battery Systems and Requirements of Puerto Rico
 Optimizing Solar Projects including Battery Energy Storage Systems (BESS)
Battery Integration with Solar Power Plants – Overview
EPRI Fall Meeting, Battery integration and Power Optimizer, Sep 29th, 20144

5. APPLICATIONS AND OPPORTUNITIES
BATTERIES (and solar projects)
EPRI Fall Meeting, Battery integration and Power Optimizer, Sep 29th, 20145

6. 6 EPRI Fall Meeting, Battery integration and Power Optimizer, Sep 29th, 2014

7. OPTIMIZING - SOLAR PROJECTS
EPRI Fall Meeting, Battery integration and Power Optimizer, Sep 29th, 20147

8. LCOE/IRR/NPV Optimization of Solar PV Plants
 We optimize for IRR, LCOE, NPV
 What are we optimizing?
 Technology
FT, SAT, 2-Axis
Mono, Poly, Thin Film, CPV
 Ground Coverage Ratio (GCR)
 Inverter Load Ratio (ILR)
 AC Size of the Plant
 Procurement support  Similar tools, slightly different concept
EPRI Fall Meeting, Battery integration and Power Optimizer, Sep 29th, 20148

9. But.. It is not an Exact Science!
 Complications:
 Accuracy of modeling efforts
 Accuracy of the meteo file
 How good are CAPEX estimates for years in the future?
 Quality of OPEX estimates
EPRI Fall Meeting, Battery integration and Power Optimizer, Sep 29th, 20149

10. PUERTO RICO EXAMPLE
Required Combining Batteries with Solar Projects
EPRI Fall Meeting, Battery integration and Power Optimizer, Sep 29th, 201410

11. PREPA (Puerto Rican Electric Power Authority) and MTRs!!
 Ramp Rate + Frequency Control
 What if these happen at the same time?
 MTRs led to a cost benefit sizing of battery
 Complex language to measure violations
 How many violations do we accept
EPRI Fall Meeting, Battery integration and Power Optimizer, Sep 29th, 201411

12. Ramp Rate Control
 The PV facility shall be able to control the rate of change of power output
 Rate of decrease of power!
 A 10 % per minute rate (based on AC capacity) limitation enforced
 Is independent of meteorological conditions
EPRI Fall Meeting, Battery integration and Power Optimizer, Sep 29th, 201412

13. Frequency Response
 The PV facility shall provide an immediate real power primary frequency
response of at least 10% of the maximum AC active power capacity
 The time response (full 10% frequency response) shall be less than 1 second
 The facility frequency response shall be maintained for at least 9 minutes
13 EPRI Fall Meeting, Battery integration and Power Optimizer, Sep 29th, 2014

14. OPTIMIZING – SOLAR PROJECTS AND BATTERIES
EPRI Fall Meeting, Battery integration and Power Optimizer, Sep 29th, 201414

15. Selecting the BESS Technology for your Project
 Lead Acid
 Low Efficiency
 Low Cost
 100% Recyclable
 Flow technologies
 Benefit from higher cycle lifetimes
 Over 4 hours do flow battery
 Break point to go to flow is 2 hours
 NaS
 High energy to capacity ratios allow performance as a
capacity resource, as backup generation to avoid
outages at remote sites, and to defer transmission and
distribution (T&D) asset upgrades on overstressed lines
and substations
 Also capable of performing frequency regulation services
 NaS and Flow
 Worse roundtrip efficiency than Li-Ion technologies
 Li-Ion
 High energy density
 Microsecond response timeEPRI Fall Meeting, Battery integration and Power Optimizer, Sep 29th, 201415

16. Contracting the BESS (Integrator and Battery Decisions)
 Can the battery supplier do the integration?
If they work with an integrator, is there a wrap guarantee?
Developer prefers one contract; with a large balance sheet
 What are their maintenance plans?
 What if BESS degrades faster than the solar field and it’s
requirements?
 If tied to a 20+ year solar PPA  Battery replacement plan
A not to exceed price
  Leads to an all inclusive NPV evaluation of suppliers in the RFP
EPRI Fall Meeting, Battery integration and Power Optimizer, Sep 29th, 201416

17. Financial Model – Accounting for Your Combined Solar and Battery
 The “round-trip efficiency” of the
battery system –
 These are losses from the solar
production
 Should be accounted for in
financial model
 While minor, batteries also
dissipate when storing over periods
of time
 Ancillary services contract
 Or take it from the grid
 Sign a utility contract
Statistical efficiency
through operating
projects
Guaranteed
efficiency
Battery (round-trip)
Inverter (round-trip)
Transformer (round-trip)
*only if vendor provide the
transformer.
Parasitic Load (round-trip)
EPRI Fall Meeting, Battery integration and Power Optimizer, Sep 29th, 201417

18. Agenda
Battery Integration with Solar Power Plants Jake McKee
Power Optimizer test results Stefan Christ
Q & A Stefan & Jake
18 EPRI Fall Meeting, Battery integration and Power Optimizer, Sep 29th, 2014

19. Three tests and three goals form the core of E.ON’s PO
testing strategy
A) Basic understanding of PO technology and suppliers’ products
B) Assessment of performance in shading conditions
C) Assessment of impact on BoS savings for large scale application
19
Retro-fit Rooftop Tests
Midsize Plant
“Retro-fit” Ground farm Test
Utility Scale
New build Rooftop Test
Residential Scale
A)
B)
B) C)
3.
1.
2.
EPRI Fall Meeting, Battery integration and Power Optimizer, Sep 29th, 2014

20. Midsize Retrofit Field Tests - Boundary Conditions
Existing commercial roof-top PV plant
 99 kWp fixed structure
 9 subfields each with 3 strings á 16 modules on 10
kVA inverter plus one 2 kVA inverter
 Inverter minimum DC voltage: 333 V
20
POs from three different suppliers tested
 2x „Buck & Boost“, 1x „Buck“ type
 For each PO supplier one full subfield equipped
 6 non-retrofitted subfields available for reference evaluation
1.
EPRI Fall Meeting, Battery integration and Power Optimizer, Sep 29th, 2014

21. Mixed performance results in regular operation
21
Pre-/Post-Retrofit Performance Comparison* vs. Reference Subfields
Overall retrofitted subfields show similar performance compared to “normal” subfields
 Disadvantage for retrofitted subfields during low yield generation
 Advantage for retrofitted subfields during high yield generation
* refers to daytime period 10 a.m. to 4 p.m.
** share of total yield: “<5 kWh”-hours approx. 36-38%, “>5 kWh”-hours approx. 62-64%,
*** valid comparison data for end of 2014 envisaged
PO 1
(Buck & Boost type)
PO 2
(Buck type)
PO 3
(Buck & Boost type)
Total 1.0% 0.0%
<= 5 kWh** -3.0% -6.0%
> 5 kWh** 4.0% 4.0%
Pre-/Post-PO-Retrofit Comparison (vs. Reference)
no valid comparison data
available ***
Criteria:
Hourly Yield*
1.
EPRI Fall Meeting, Battery integration and Power Optimizer, Sep 29th, 2014

22.  Only sunny days used for near shading performance testing
 “Extreme” shading conditions, i.e. no diffuse irradiance on shaded cells
 Several shading scenarios relevant for utility scale plants simulated, e.g.
A) Row-to-Row shading for landscape module orientation
C) Several single shading objects in each string
 PO advantage vs. shaded reference ranging
0-35% for Buck & Boost
0-21% for Buck only
22
C)
PO 1
(Buck & Boost type)
PO 2
(Buck type)
PO 3**
(Buck & Boost type)
Shaded
Reference
A 77.0% 41.5% 76.5% 42.0%
C 76.5% 71.5% 74.5% 50.5%
Shading
Scenario
Subfield Yield vs. non-shaded Reference*
* Shading tests results refer to a single day for each shading scenario; Comparison normalised, refers to daytime period 10 a.m. to 4 p.m.
** only very limited pre-retrofit data available
Good performance results in near shading conditions1.
A)
EPRI Fall Meeting, Battery integration and Power Optimizer, Sep 29th, 2014

23. Comparative tests being performed on
East-West-rooftop in Germany (1 out of 5 test sites)
modules with PO
modules without PO
PV System A PV System B
POs: 24 DC/DC Optimiser no PO
Module Type: 240 Wp mono Si
Modules allocation: each 12 East / 12 West
PV capacity: each 5.8 kWp
Inverter: each 3.7 kW, 2 MPPT
23
2.
EPRI Fall Meeting, Battery integration and Power Optimizer, Sep 29th, 2014

24. Performance impacted by a tree’s shadow in afternoon
25th March 2014
 Power optimisers’ positive impact on output in near shading
condition
West side observation
20th March at 4.20 p.m
24
2.
EPRI Fall Meeting, Battery integration and Power Optimizer, Sep 29th, 2014

25. Some time later the shade is gone and so is the
DC/DC advantage
19th May 2014
 Continuous slight underperformance of PO equipped system when
no nearby shading occurs
25
2.
EPRI Fall Meeting, Battery integration and Power Optimizer, Sep 29th, 2014

26. Monthly performance does not show a Power
Optimizer advantage
Monthly production
26
2.
EPRI Fall Meeting, Battery integration and Power Optimizer, Sep 29th, 2014

27. Summary of current PO testing
Results & Findings:
 Test setups and provided no evidence for performance
enhancement by POs in conditions with no near shadings
 Performance enhancement by POs in near shading conditions observed
Next Steps:
 Tests in large scale utility ground farm will focus on BoS optimization
 Ongoing discussions with PO suppliers about further technology
optimization
27
1. 2.
3.
EPRI Fall Meeting, Battery integration and Power Optimizer, Sep 29th, 2014

28. Thank You..
Questions?