solar power

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Application of Solar Power in Jamaica Anthony Chen Climate & Energy Technology Group Department of Physics UWI, Mona

http://wwf.panda.org/what_we_do/footprint/climate_carbon_energy/ene rgy_solutions/renewable_energy/sustainable_energy_report/

Energy Independence Using Renewable Energy • Energy Independence – having own source of energy, no depencence on others • Once Renewable Energy exceeds 20 -30% of energy mix, fluctuatuons in renewable energy sources become a problem – Winds die down, clouds block solar radiation – Electricity supply fluctuates • Cannot meet demand

• A way of firming energy to back up fluctuating supply necessary

Firming Energy – Pumped Storage • Pump water to elevated storage reservoir in times of excess renewable energy and recover by gravity in down-time or continuous basis • Drawback – additional cost of building a reservoir and generator. • Cost offset: – Use reservoir to aid water management

Pumped storage facilities

Japan's Sea Water Pumped Storage Iberdrola's 635-megawatt La Muela pumped storage facility

Firming Energy - Combined cycle gas turbine • • • •

Run at low power (50%) Easily brought up to full power Spinning reserve inefficient

Firming Energy - Hydrogen • Renewable-sourced electricity from diverse sources, can be converted to hydrogen and oxygen – high-pressure-output electrolyzers

• Hydrogen pipelined to load centers (cities, refineries, chemical plants) – used as vehicle fuel, combined-heat-andpower generation on the retail side of the customers’ meters, ammonia production, and petroleum refinery feedstock.

In addition Prediction of Wind and Radiation • Avoid surprizes • Know hours before when wind or radiation will go down • Bring spinning resreve up in time

Enough land for Solar? • Daily energy consupmption by Jamaicans – 13700 MegaWatt-hours • Assume daily amount provided by other RE (mainly wind) – 3200 MegaWatt-hours • Assume daily amount to be provided by solar – 10500 MegaWatt-hours

How much solar radiation in Jamaica? Soalr Radiation Map

Dept of Physics UWI Sponsored by PCJ

1994

Based on radiation measurement at 12 stations

Extrapolated to grid points over Jamaica

• Average radiation in Jamaica – 0.005 MegaWatt-hour/sq.meter (from UWI map) • Assume efficiency of solar energy device ~ 20% • Average energy produced by solar device – 0.001 MegaWatt-hour/sq.meter • Land area required = 10500/0.001 sq meter – 10,500,000 sq meter • Total land area of Jamaica – 1,100,000,000 sq meters • Fraction of land needed ~ 1/1000

Solar Applications • Domestic – Water heating (costing) – Photovoltaic (PV) (costing) – Solar cooling

• Large scale – – – – –

PV farms Solar tower Parabolic Trought Fresnel Mirror Stirling Dish engine

Domestic Solar • Water heating and crop drying (nonelectric) • Photovoltaic – Grid tied – Stand alone

Solar Thermo-syphon Cycle

ENERGY AUDIT of MARY SEACOLE HALL UWI, MONA A P33M PRESENTATION BY: NNYEKA PRESCOD 04-091923 SUPERVISOR: PROF A. ANTHONY CHEN

WATER HEATING a) HEAT ENERGY ON MSH For each student 11.8kg x 250 students= 2950kg of hot water Twice a day 2950kg x 2 = 5900kg of hot water Heat Energy Required for Heating showers: Q = mcΔT … (1)  Q = 5900kg x 4190J/K/kg x (339-291)K  Q = 1187 MJ … (2)

Electric Heating vs. Solar Water Heating Total cost: installation and maintenance of a solar water heating system over 20 years:

$10 500 000.00JMD Total cost: Installation and maintenance of electric water heating: $32 269 484.44JMD Over a 7 year period, the initial payment for the Solar Water Heating system will be amortized. Energy consumption is reduced by 39%. Savings = $144 866.86 per month and $896 361.24 in O and M costs over a 20 year period

Photovoltaic (PV) Cells/Solar Cells

Basic unit is a PV cell Modules: a set of cells arranged in series Array: a collection of modules

An array of 4 PV modules

On a roof top

Stand Alone 24 Volt system, not connect to grid

Grid-tie 48 Volt system without battery backup

Grid-tie 72 volt system with battery backup

Overall loss of energy in PV for Grid tied system without backup batteries: Rated Energy from PV at 25 C Energy reduced over lifetime due to aging Energy reduced due to operation at 50 C Energy remaining after conversion into AC by inverter

Compare JPS with Grid Tied PV over 30 year lifetime (no loan involved) JPS • US 40¢/KWH

Grid Tied • US 17¢/KWH

If JPS rate inflated at 3% annually, then system would payback for itself in 11 years with approximately 19 years of free electricity

Overall loss of energy in PV for Stand alone system Energy from PV at 25 C Energy reduced over lifetime due to aging Energy reduced due to operation at 50 C Energy reduced due storage in battery Energy remaining after conversion into AC by inverter

Compare JPS with Stand Alone PV (No loan involved) JPS • US 40¢/kWh

Stand alone • US 55¢/kWh

Stand alone does not offer economic advantage Assumes that JPS rates will not increase Very unlikely

Advantages include Insurance against total blackout – enough for lighting

No fuel cost Except for battery replacement, little maintenance required.

Some conclusion re PV • Photovoltaic grid-tied systems betters JPS supplied electricity if net metering is allowed. • A stand alone PV system can also be promoted as back up system and would compare favourable with a gasoline or gas generator. • A more urgent and compelling case and national programme of action is required for renewable energy – Net metering, Net metering, Net metering ......

Large Scale Solar systems • PV Solar Farms • Solar Thermal – Power tower

– Parabolic Trough

– Stirling Dish Engine Also Fresnel Mirror System

PV Solar Farm

• Monday, June 06, 2011 • Fotowatio Renewable Ventures to build a 20 megawatt solar photovoltaic farm near Las Vegas, Nevada. • More than 90,000 solar panels with singleaxis horizontal tracker technology that will allow it to follow the sun • 55,000 megawatt hours annually, enough to power over 4,700 homes.

Satcon™ Equinox™ 625 kW PV inverter

Specification

Inverter Specs (cont.)

Efficiency of PV Plant • Efficiency in term of ratio of electrical energy output to solar energy input limited mainly by efficiency of PV panels • Less than < 20%

Argument Against Multi-MW PV Farms • For a multi-Mega Watt plant located at one place, it necessary to transport power at great cost to places where it is required. • On the other hand Solar energy can be collected anywhere so we have a potential to generate power where it can be used • Solar energy is therefore ideal for distributed power generation, thus saving line losses in transporting power at hazardously high voltages.

Argument (cont.) • Biggest problem with the multi-MW solar PV plant is that it loses 12-15 percent of expensive power as it passes through a series of power transformers. • In MW plants PV solar inverters generate power at ~ 400V three-phase, then stepped up to 66kV, then stepped down to 400V with another string of transformers to suit consumer requirements. • Also likely transmission loss of 5-7 percent in the power grid. • Why suffer an avoidable 20 percent loss of expensive solar power when smaller solar plants with close proximity to their users incur no energy loss during transmission

Parabolic Trough

Principle of operation • Parabolic trough power plants use concentrated sunlight focused on a receiver tube located at the focus of the parabolic shaped mirrors • A heat transfer fluid (e.g., oil) passes through the receiver and is heated by the concentrated rays to temperatures (400ºC) • The hot fluid transfers heat at a heat exchanger to produce high pressure steam used drive a conventional Rankine cycle steam power plant • These plants use a large field of parabolic trough collectors which track the sun during the day

Parabolic Trough Power Plant

Efficiency of parabolic trough plant • Limited mainly by efficiency of steam turbine • Less than 40%

Solar Tower

Principle of Solar Tower • Power towers capture and focus the sun's thermal energy with thousands of tracking mirrors (called heliostats) in roughly a two square mile field. • A tower resides in the center of the heliostat field. • The heliostats focus concentrated sunlight on a receiver which sits on top of the tower. • Within the receiver the concentrated sunlight heats molten salt to over 1,000 F (538 C). • The heated molten salt then flows into a thermal storage tank where it is stored, maintaining 98% thermal efficiency, and eventually pumped to a steam generator. • The steam drives a standard turbine to generate electricity. • Uses the Rankine cycle similar to a standard fossil fuel power plant

Solar tower thermal power plant

Efficiency of Solar tower power plant • Limited mainly by efficiency of steam turbine • Less than 40%

Advantages/Disadvantages • The advantage of this design above the parabolic trough design is the higher temperature. • Thermal energy at higher temperatures can be converted to electricity more efficiently • Thermal energy can be more cheaply stored (in salt solution) for later use. • Furthermore, there is less need to flatten the ground area. In principle a power tower can be built on a hillside. • Mirrors can be flat and plumbing is concentrated in the tower. • The disadvantage is that each mirror must have its own dual-axis control, while in the parabolic trough design one axis can be shared for a large array of mirrors.

Fresnel Mirror System

Principle of Fresnel Mirror System • Fresnel mirror systems are similar to parabolic trough but use long flat mirrors at different angles to concentrate sunlight on to a tube containing heatcollecting fluid. • A linear Fresnel reflector power plant uses a series of long, narrow, shallow-curvature (or even flat) mirrors to focus light onto one or more linear receivers positioned above the mirrors. On top of the receiver a small parabolic mirror can be attached for further focusing the light. • These systems aim to offer lower overall costs by sharing a receiver between several mirrors (as compared with trough and dish concepts), while still using the simple line-focus geometry with one axis for tracking.

Schematic

Stirling Dish Engine

Principle of Operation • A dish stirling system uses a large, reflective, parabolic dish (similar in shape to satellite television dish). • The dish tracks the sun and focuses all the sunlight that strikes it onto to a single point above the dish • A receiver (the heating element of a Stirling engine) captures the heat at that point • The heat is converted into mechanical work by a Stirling engine • Used to drive a generator to produce electricity • The entire unit acts as a solar tracker

Schematic

thermodynamic cycle for stirling engine 1: isothermal (constant temp TH) expansion, Heat added to working fluid 2 : gas cooled at constant volume from temp TH to TC, (Heat rejected) 3: isothrmal (constant temp TC) compression, Heat rejected

TH

TC

4: gas heated at constant volume from temp TC to TH (Heat added)

Ideal Efficiency = TH -TC TH The higher the value of TH, the more efficient the engine, controlled by the amount of radiation on the heating element

Ideal Stirling cycle

http://wiki.protospace.nl/index.php/Stirling_Cycle

Alpha type Stirling Engine 2

http://dekkeraero.com/Reseaarch_Projects_Page_2.html

Efficiency • Efficiency limited by the efficiency of the Stirling Engine • E ≤ 40%

Advantage • Does not require a steam turbine, like parabolic trough and solar tower • Can come in smaller units

Disadvantages • Heat to electricity conversion requires moving parts and that results in maintenance. • The (heavy) engine is part of the moving structure, which requires a rigid frame and strong tracking system. • Parabolic mirrors are used instead of flat mirrors and tracking must be dual-axis.

Clean Hydrogen Water Cracker (High Temp) H2O → O + H2 → H Fuel Cell

List of solar thermal plants *List of Solar Thermal Power Stations.doc

Some conclusion • Energy system dominated by solar energy is possible • Long term planning necessary – A roadmap needed

• Can lead to energy security and even energy independence

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