Sustainable Energy Futures for Small Communities

summery of the talk by Ken Mitchell
given at Hampden community hall on 16/11/2007




Electricity Consumption in NZ

Domestic Household – 8000kWh p.a.
Europe – 4000kWh – more use of gas
Most energy used for Thermal applications
Most electricity is renewable (CO2) - hydro
Minimal storage or diversity – pricing risk
Centralised system – high line investment
Cheap abundant generation – low efficiency BUT completely unsustainable





Old Verses New






Demand

Demand drives power system investment
Design for peak demand – all electric house standard connection is 15kVA
In areas where assets can be shared – design for 5kVA per connection
100% average demand of a 8000kWh p.a. house is only 1kVA or 22kWh/day
Household demand exceeds 5kVA for a duration of 5%





Hampden

Feeder – 481 consumers 90% residential
50% in Hampden av. 24h demand 700W
Feeder MD 430kVA ADMD 340kVA
15km 33kV + 65km 11kV + 2818kVA Tfmr
9 distribution tfmrs supplying 240 consumers 10km LV
12% capacity utilisation – holiday homes





At what cost?

MEL retail charges p.a. for 8000kWh
$1761.47 = 22c/kWh
MEL low user 4000kWh (15% consumers)
$911.28 = 23c/kWh (28c/kWh hol. homes)
Close to diesel genset cost – not cheap!
System Operating costs - $100k
240 consumers – supporting $2.1M capex
Actual investment higher but subsidised – hurdle for change – pricing policy supports status quo





Big Opportunity

We are installing 3 times the amount of asset needed to service the top 5% of demand
If we live with 5% less utility (below 5kVA) then there will be much less power system investment needed.
If we reduce demand to 1kVA then we don’t need any more power system than localised 230V interconnection





Diversity is Key

Load with multiple energy sources and storage – water, heat, wood, gas, batteries
Diverse generation portfolios' in diverse locations
Distributed generation & active networks
Balances supply risks – no price shocks
Isolates from price path associated with unsustainability





Planning for the Future

Peak Oil tells us that by 2050 the worlds energy consumption will be at 1960’s level but population will be 3 times larger.
Most houses that will exist in 2050 have already been built
All the technology that will let us live in a lower energy scenario already exists and is economic to retro-fit now





Low Energy Homes

Can already keep demand below 5kVA with no more loss of utility than living off a water tank
Homes with diversity - low energy lighting, gas cooking, solar hot water and/or log burner space heating – 2000kWh 2kVA – just through choice of appliances not use
Add storage/batteries - 1kVA – next step zero emissions





Zero Emission Homes

Add insulation, PV cells, small turbine
And/or add DG at community scale
20-50 homes 100kVA interconnect at LV
Min 2 different generators of 100kVA for base load
Eg. Windmill and biodiesel genset (firm)
No 11kV power lines, transformers, or redundant asset for security





Not just Electricity

Water, waste water, storm water – 3 sets of infrastructure
There is sufficient solar energy falling on the roof of garage p.a. to power an electric car – NZES 60% by 2050 - communal
Can share hot systems and batteries also
No infrastructure means no bills – not an issue of cost just different choice of solution – benefit if lower cost





Sustainable Community Power Supply Options

Best gains from integrated community wide solutions.
Design as discrete communities – don’t make too large/inclusive – intensity is important
Look holistically at all energy and waste issues – they are the solutions to each others problems – heat from genset usable – host loads
Food and food production are energy issues
Glasshouses, waste heat, load dumps, ice bank
Grey water irrigation, compost sludge – low tech





Community Level System

50% base load – hydro, biomass, geothermal
25% Peaking (2h) Firming (8h) – bio gas/diesel
25% Variable - wind, PV
15% Storage – batteries, hydro, pumped, heat
25% DSM – load control, fuel switching
Load Dumping – pool, glasshouse, school
Can stage implementation – retain grid connection – allows other initiatives priority





Can this be done in Hampden for less than $2.1M?

Wind turbine 225kVA $300k
Diesel Genset 350kVA $150k
Hydro/Irrigation? 100kVA $250k
PV 50kVA $250k
Batteries/charger 3000Ah $20k
LV Reticulation $400k
Controls, buildings, etc $80k
Conventional system total $1.45M





Will this meet consumption?

240 users @ 4000kWh 960,000kWh
Wind 200kW 6h/day 438,000kWh
Hydro 100kW 8h/day 292,000kWh
PV 50kW 8h/day 146,000kWh
Diesel shortfall 84,000kWh
@ 300kW = 280h p.a. 1h for 6 days/week
Alternative to PV and Diesel – trickle charge off network





Enablers

Community will and buy-in
Life-style choices - Living with 4000kWh
Appliance choices when renewing
Equitable sharing of costs/benefits
Power company participation – capital, reuse of reticulation, design and operating know how
Exporting surplus if resources available