Photovoltaic, solar power and HTS technologies

- status and trends

A.Hunze, R. Badcock,

A. Gardiner, A. Caughley

Industrial Research Limited

Superconductivity and Energy group

Arvid Hunze

Industrial Research Limited

Superconductivity and Energy group

Mail : a.hunze@irl.cri.nz

Web : www.irl.cri.nz

Outline

• The problem (as far as I understand it) – and possible solutions

• Photovoltaic technology – status and trends

• Hydrogen storage for PV – status, trends and NZ experience

• Solar thermal – a brief intro

• HTS opportunities - extremely high power density power cable, generators, cryogenic

systems and RF (long hand) filters

The SKA power problem

– as far as I understand it …How to guarantee …

- power supply and relatively flat load 24/7 in the order of 80-100 MW at the main site

- in one of the most remote areas of the world

- with high (direct) solar radiation and also high temperature values and differentials

- a radio quiet environment is maintained

- a low CO2 footprint, using renewable energy sources up to 100 %

- power of 1 MW at the smaller sites / outer stations

- and a solution that is not too expensive (of course)

Photovoltaic, Solar Power

and Storage

Generating technologies - options

“Both candidate SKA sites are, in fact, exceptionally well placed to use solar-based

generating solutions, provided cost and storage issues are adequately addressed. Early

consideration of solar technologies, including relatively new concentrating solar voltaic

systems, indicate that such solutions may be feasible, given a willingness to invest in a suitable-

scale development program and, most probably, to subsidize the unit cost of SKA renewable power,

at least for the period of the instrument's operational life in which fossil-fuel alternatives are priced

relatively attractively..”

Power Considerations for the Square Kilometre Array (SKA) Radio Telescope

Peter J Hall, 2011 IEEE

Solar PV technologies – Overview

Crystalline Si (wafer)

Thin Film Silicon

Thin Film II – VI

Thin Film III – V

Concentrated PV

New Materials

Monocrystalline (c-Si)

Polycrystalline (c-Si)

Amorphous (a-Si)

Microcrystalline (µc-Si)

Ta

nd

em

/Tri

ple

CuInGaS(e)

CdTe

GaInP / GaAs (2J)

InGaP / InGaAs / Ge (3J)

Organic

Printed PV

Dye Sensitized

… (xJ)

Silicon Wafer, “classic PV”

“Thin Film (Silicon) PV”

a-Si, “micromorph”

“Thin Film PV”

Multijunction cells on III-V group

materials (“inverted LEDs”).

Organic and hybrid materials

Printed semiconductors

Maturity level still very low.

Typ. in field eff.Max. lab.

eff. Low light (dirt)

Temp.

coeff. [%/K]Status and trends

c-S

i

15 % (multi)

20 % (mono)

20.4 % (multi)

25.0 % (mon)

(wafer)++ -0.4 %/K

Std. technology with largest production capacity

worldwide

TF

-Si

10 % 12.5 % ++ - 0.3 %/KImproved efficiency potential with multiple and

micromorph technology.

Cd

Te 11% 17.3 % + - 0,25 %/K

Todays cheapest module technology, but

size limitations due to fabrication process, max GW

limitations due to Te scarcity and end product contains

toxic elements.

CIG

S 12 % 20.3 % 0 -0.4 %/K

Highest efficiency potential of all non-concentrated

technologies, but still no high volume production

process.

CP

V 25% 43.5 % (cell) - -0.2 %/K

Highest efficiency (potential) of all technologies, but

still between R&D and production stage. Requires

light focusing thus high direct normal radiation and

sun tracking.

For high direct normal irradiation and high temperature sites

CPV seems to be best technology choice

esp. with further improvements in the future

Solar PV technologies – comparison

Optical efficiency :

100% x 80 % = 80 %

concentrated light energy

on cell lost due to :

- light reflection

- optical losses at interfaces

- light way misalignment

Start :

100 %

sun light in

Cell effciency :

100% x 80 % x 40 % = 32 %

conversion loss of light energy

to electrical energy due to :

-incomplete spectrum

conversion

- cell temperature loss

Sunspectrum

and 3 layer

absorption

InG

aP

GaA

s

InG

aA

s

Cell to module on tracker :

100% x 80 % x 40 % x 90 % = 30 %

electrical energy loss due to :

- wiring

- module array on tracker

Module

Concentrated PV – How it works

Optical

Also DNI is higher in the

desert

Start

This is good

in the desert

Cell

High T in the desert but lowest T

loss of all PV technologies

Sunspectrum

and 3 layer

absorption

InG

aP

GaA

s

InG

aA

s

Tracker

Tracking enables better and more flat

generation profile

Module

Concentrated PV – what are the advantages

Optical

Due to focusing sensitive to

contamination and dust

so regular cleaning might

be an issue (DI water).

Start Cell

Sunspectrum

and 3 layer

absorption

InG

aP

GaA

s

InG

aA

s

Cell

Tracking = mechanical movement

always sensitive, good maintenance

required

… and it will not work at night

combination of technologies or

storage required

Module

Concentrated PV – what is challenging

PV and storage in the NZ context

ENA Solar CHCH – Inverter

Might be some special needs in CPV

due to fluctuations/ spikes when alignment not perfect, clouds passing …

Storage options

Source: EPRI Study on Commercial Energy Storage

~1 GWh (80 MW/12h) off grid

storage needed with strong

discharge cycles

high energy density storage

so pumped hydro () and CAES worse

options

deep discharge cycles challenging

for most battery technologies

Hot environment

battery technologies

suffer severe heat degradation

problems

Low costs and “proven” technology

hydrogen storage

seems viable option

HYLINK (hydrogen link) concept - IRL

The concept

Storing renewable electrical energy using hydrogen gas

Invisible underground gas pipe (no overhead wires, ~ 1MW easily handled by a single pipe)

Only one other installation worldwide (but not renewable or remote)

The benefits

Good solution for locating renewable energy sources in optimal positions, transport H2

instead of electrical power

could be beneficial for reduced noise

Pipeline cheaper than installing overhead wires for lengths >2km

Pipe part of the volume for energy storage

hydrogen

Fuel

cellelectricity

hydrogenHouse

Grid

• 16mm gas pipeline (MDPE)

provides energy transfer (1MW

capable) AND storage.

• Buried pipeline cheaper than

overhead cables when >2km and

cheaper than batteries.

• Minimal resource consent issues,

invisible, long life

HYLINK example - Totara Valley site

Valley: peak demand smoothed

electricity

• Electrolyser

– Test site for a new in-house design

• Alkaline bipolar cells, 4 barg

• 24V, 100A input

• Fuel cell system

– Field prototype from ITRI, Taiwan

– 2kW, 24V low pressure PEM

• Hydrogen burners (planned)

– Investigate H2 and H2/LPG blending

• Hydrogen distribution and storage

– 315mm dia, standard polymer fuel pipe

– 8kWh HHV at 4 barg

– Inclined moisture purging

– Buried in raised garden

Concentrated solar power - overview

- different technologies but apart from parabolic dish no long term experience

- big advantage over PV is inherent storage possibility

but only experimental technologies can provide full 24 h operation

(e.g. oil vs. molten salt)

Efficiency (%) + -

Pa

rab

olic

15-20 %

most established technology

(> 90 % of installations)

easy to scale

1 axis tracking

flattened area

high water usage

Fre

sn

el

experimental

potentially lower cost

lower complexity

1 axis tracking

R&D stage

efficiency

shadowing

larger area needed

To

we

r

17 %

higher temperature thus higher

efficiency potential

direct steam integration easier

pilot stage

2 axis tracking for every mirror

flat area

Dis

h 30 %

higher temperature, high efficiency

decentralized independent units

(like CPV)

pilot stage

high complexity

(energy unit attached/moving)

no storage possibility

high maintenance

For high direct normal irradiation and high temperature sites

concentrated solar could be viable option

but less experience/ installations than PV

Concentrated solar power – comparison

High temperature superconductivity

and cryogenic refrigeration

Status and trends

• Copper Cables

Equivalent HTS Cable

High Temperature Superconducting Cable

GCS

HTS power cable

Long Island, New York.

609 meter cable system

138 kV, 574 MW

Operating since April 22, 2008

Participants: AMSC, Nexans, Air Liquide,

LIPA

HTS power cable could be viable option for parts of the SKA :

- much higher power density at low impedance

- can be buried underground (safety, noise)

- higher and T-independent efficiency

- inherent fault current limiting properties, reducing damage propagation

- due to constant cooling better lifetime than conventional expected

574 MW

AMSC

Conventional Generator HTS Rotor with air-gap winding stator

(High power density)

a/2

• Smaller footprint/mass

• Higher efficiency at lower load

• No ageing in the rotor expected

• Improved electrical stability, potential to

reduce inductance whilst increasing

current density

• Power rating 100%

• Ageing rotor winding

• Limited power diagram

a

Benefits of Superconducting Utility Generators

Siemens

Converteam

IRL Cryogenic Refrigeration R&D Experience

• Underlying science & capabilities

– Cryocooler design and manufacture.

– Modelling of oscillating thermodynamic systems.

– Computational Fluid Dynamics.

– Cryogenic materials, properties and use.

– Cryogenic Engineering.

– Flexible membrane (diaphragm) design.

– Reciprocating and rotating machinery design.

– Pressure vessel design.

• Diaphragm Pressure Wave Generator technology.

– Unique double metallic diaphragm technology overcomes shortcomings of incumbent technologies.

– Scalable from 500W-30kW input power.

• Pulse Tube Cryocoolers.

– Development of medium to large (10-1000W) pulse tube cryocoolers.

Experience of cryogenic refrigeration systems

might be interesting for custom tailored receiver cooling solution

HTS RF filters

Opportunities for HTS solutions

for high Q RF filters to be explored

• much lower surface

resistance than conventional

materials

• planar design possible

• already tried in deep space

network project for

interference mitigation

HIGH TEMPERATURE SUPERCONDUCTING 8.45-GHz BANDPASS FILTER FOR THE DEEP SPACE NETWORK* G. L.

Matthaei** and G. L. Hey-Shipton (1993)

Summary

• Concentrated PV + Hydrogen storage and/or solar thermal power plant are good

options for powering the SKA but still many challenges on the way

• PV and CSP opportunities for NZ to be explored

• Strong NZ capabilities in Hydrogen storage - HYLINK concept

• Strong NZ capabilities and industrial partnerships in HTS systems that could be

useful for

- underground HTS power cables

- higher efficiency HTS generators (e.g. in a solar thermal plant)

- tailored cryogenic solutions for receiver cooling

- HTS RF filter opportunities

Thank you very much

for your attention