Solar energyEnergy Centre summer school in Energy Economics

12-14 April 2021

Kiti Suomalainen

k.suomalainen@auckland.ac.nz

Outline

The resource

The technologies, global deployment & costs

Solar research at the Energy Centre

The resourceWORLD ENERGY USE (2015):18.5 TWy/y

RENEWABLES [TWy/y]:Solar 23,000Wind 75-130Waves 0.2-2OTEC 3-11Biomass 2-6Hydro 3-4 Geothermal 0.2-3++Tidal 0.3

FINITE [TWy]:Nat. Gas 220Petroleum 335Uranium 185++Coal 830

• Sun > 1000 x world energy demand• 6 hr of sun ~ 1 yr of world energy demand• All petroleum < 4 days of sun• All coal ~ 2 weeks of sun

Source: https://www.iea-shc.org/data/sites/1/publications/2015-11-A-Fundamental-Look-at-Supply-Side-Energy-Reserves-for-the-Planet.pdf

Capturing solar energy

• Heat – through absorption

• Pools & sanitary water

• Drying (water evaporation) e.g. crops, other foods

• Passive space heating

• Mechanical work -> electricity (solar thermal electricity / concentrating solar power)

• Photoreaction

• Photovoltaic (PV) effect

• Photosynthesis

1) Solar PV2) Concentrating Solar Thermal Power3) (Solar Thermal Heating and Cooling)

Solar photovoltaics (PV)

• Absorption of incident photons to creates electron-hole pairs.

• Electron-hole pairs will be generated in the solar cell (provided that the incident photon has an energy greater than that of the band gap).

• The pair is separated due to the electric field existing at the p-n junction -> electrons flow one way, holes the other

Solar PV in the world

Sources: REN21, (2019, 2020), Renewable Energy World (visited Feb 2021),https://www.renewableenergyworld.com/solar/142-gw-of-solar-capacity-will-be-added-to-the-global-market-in-2020-says-ihs/#gref

2019

2018

Solar share in electricity:Honduras 10.7%, Italy 8.6%, Greece 8.3%, Germany 8.2%, Chile 8.1%(China 3%)

2019:+115GW

2020:+142GW?

Side note: Floating PV

• First FPV 20kW in Japan 2007

• Now in at least 29 countries• Benefits:

• Increase potential where land is limited

• Improved output (cooling effect, less dust)

• Reduced evaporation• LCOE similar to ground-

mounted (slightly higher cost, slightly higher yield)

• (Vietnam announced pilot auctions for 400MW in 2020)

2019: 2.4 GW

Sources: REN21, (2019, 2020)

PV cost trends

Source: IRENA, (2019), IRENA webinar: https://www.irena.org/-/media/Files/IRENA/Agency/Webinars/2020/Jun/IRENAinsight-webinar_RPGC-in-2019-Overview.pdf?la=en&hash=80A08A29C8807989DC9DBA8E78E55B6124DC5E42

Average monthly European solar PV module prices by module technology and manufacturer, Jan 2010–Jul 2018 (top) and average yearly module prices by market in 2013 and 2018 (bottom)

Cost reductions 2010-2019:Module: 52%Inverter: 10%Racking, mounting: 7%Other BOS hardware: 3%Installation: 13%Other: 15%

Concentrating solar power (solar thermal electricity)

• Generating solar power by using mirrors or lenses to concentrate a large area of sunlight, or solar thermal energy, onto a small area.

• Electricity is generated when the concentrated light is converted to heat, which drives a heat engine (usually a steam turbine) connected to an electrical power generator.

Concentrated solar power with storage

https://www.solarpaces.org/how-csp-thermal-energy-storage-works/

Concentrated solar power in the world

Source: REN21, 2019.

CSP cost trends

Source: IRENA, 2019.

Total installed costs of CSP plants by technology and storage duration, 2010–2018

IEA’s Sustainable Development Scenario tracking

On track x Not on track

Largest solar power plants

(45 MW)

“the largest single-site project will generate 700 megawatts (MW) of power when completed”

Largest solar power plants

Largest solar power plants

Highlights:• Project will reduce Abu Dhabi’s CO2

emissions by 1 million metric tons• That's equivalent of removing

200,000 cars off the roads

Largest solar power plants

Solar hot water globally

Solar Water Heating Collector Additions, Top 20 Countries for Capacity Added, 2019

Solar Water Heating Collector Global Capacity, 2009-2019

Source: REN21, 2020.

Solar research at the Energy Centre

Solar potential of Auckland rooftops using LiDAR data

Detailed analysis of solar vs. demand

Collected by NZ Aerial Mapping and Aerial Surveys Limited for Auckland Council in 2013/2014.

Flight info:Altitude 900m, 1600m, 1000mScan frequency 36Hz, 45Hz, 42.9Hz

Average point spacing: minimum 1.5 points per m2

Vertical accuracy: +/-0.1m

Solar potential in Auckland rooftops using LiDAR data

Solar webtool: solarpower.cer.auckland.ac.nz

Detailed analysis of solar vs. demand

in one neighbourhood

• New approach:

• Measured solar radiation data

• Metered demand data

• Tested on 1 suburb: Pinehill

• Roughly 1000 houses ~600 matched with demand

Pinehill, Auckland

Solar radiation data

• NIWA 12*24: 12 typical days, one per month

• NIWA 8760: typical meteorological year of hourly data

• CliFlo: measured global radiation at 10min time resolution for 2015

Month

Wh

/m2

/day

Daily solar radiation at weather station

PV output• 5 kW PV system on all roofs

• NIWA ‘typical meteorological year’ solar radiation data

• Summer: roof orientation defines peak

• Winter: sun lower -> more impact from shading by nearby objects

Solar vs. electricity demand

Total annual PV output:

3.3 GWh

Total annual demand:

2.8 GWh

Quite a mismatch!

Demand data

Aggregated demand over Pinehill (top)

vs.

Average demand from individual households (middle)

vs.

Actual demand from individual households (bottom)

Self-consumption vs. selling to grid

3 example houses

ORANGE: PV outputGREEN: DemandRED: PV self-consumedBLUE: PV sold

Demand vs. solar dynamics

BLACK: PV outputRED: PV consumedBLUE: PV sold

Large share of PV generated is unused by PV owner.

Economics of PV per household

Assume for household:

• Buy: 25c/kWh

• Sell: 8c/kWh

12 c/kWh

16 c/kWh

BLACK: annual bill without PV

RED: annual bill after savings from self-consumption

BLUE::annual bill after self-consumption and selling excess back to grid

At ~7 MWh annual demand you can roughly halve your annual bill.

Economics: Annual revenue

Savings from self-consumption

Revenue from selling excess to grid

Long-term economics: Net present value (NPV)Discounted

annual revenues

Investmentcost

Inverter replacement

(yr 15)

Discounted annual O&M

costs

Net present value

Assumptions:

Panel annual degradation rate: 0.995Price of electricity: 0.25 c/kWhPay-back rate: 0.08, 0.12, 0.16 c/kWhPV system investment cost: $3000/kWInverter replacement cost: $400/kWAnnual O&M cost: $20/kWDiscount rate: 0.03, 0.05, 0.07Lifetime: 20 years

Next steps & take-home messages

• Understand impact of different solar radiation data sources

• Expand analysis to different neighbourhoods

• Understand optimal PV sizing & battery placement; impact of aggregation

• Residential sector provides unutilised roof space: How is that best utilised?

• Timing matters: Residential solar economics

• Prosumer opportunities matter: How can you sell at a better price?