epri q3 2014 meeting - batteries & power optimizers
TRANSCRIPT
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
Agenda
Battery Integration with Solar Power Plants Jake McKee Power Optimizer test results Stefan Christ Q & A Stefan & Jake
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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.
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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
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APPLICATIONS AND OPPORTUNITIES BATTERIES (and solar projects)
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OPTIMIZING - SOLAR PROJECTS
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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
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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, 2014 9
PUERTO RICO EXAMPLE
Required Combining Batteries with Solar Projects
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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
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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
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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
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OPTIMIZING – SOLAR PROJECTS AND BATTERIES
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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 time EPRI Fall Meeting, Battery integration and Power Optimizer, Sep 29th, 2014 15
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
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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)
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Agenda
Battery Integration with Solar Power Plants Jake McKee Power Optimizer test results Stefan Christ Q & A Stefan & Jake
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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
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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.
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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
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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.
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Mixed performance results in regular operation
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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.
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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
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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%
ShadingScenario
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 conditions 1.
A)
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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
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2.
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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
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2.
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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
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2.
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Monthly performance does not show a Power Optimizer advantage
Monthly production
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2.
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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
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1. 2.
3.
EPRI Fall Meeting, Battery integration and Power Optimizer, Sep 29th, 2014
Thank You.. Questions?