Electric Power Optimization Centre
GEMSTONE is the name we give to the EPOC project that aims to
develop a zero carbon energy system for New Zealand. The core problem
underlying GEMSTONE is to determine the scale and timing of investments and
shutdowns of electricity generation over a long time horizon.
GEMSTONE entails a suite of different models at different time scales:
POUNAMU (html)Daily operation to deal with renewable intermittency.
JADE (html)Medium-term operation to deal with dry-year risk.
EMERALD (html)Long-term investment in generation capacity.
Security of Supply in the New Zealand Electricity Market (report) (literature survey)Ben Fulton ‒ December 18, 2018The New Zealand Government recently announced that the nation's electricity should
be entirely produced by renewable sources 'in a normal hydrological year' by 2035. As
a result, power stations that use coal and gas are being phased out, the largest of which
is Huntly Power Station. This report examines the effect of Huntly's units being shut
down, and how the potential deficit in supply could be resolved.
To do this, policies of when and where to release water from New Zealand's seven
largest reservoirs and how much electricity to produce by thermal means are constructed
using Stochastic Dual Dynamic Programming. These policies are then simulated using
historical data which captures the weekly inflows of water into each of the reservoirs. The
various policies and simulations represent various combinations of electricity-producing
units at Huntly being available, as well as renewable energy sources being added into the
New Zealand Electricity Market.
Huntly Power Station (Huntly) has both coal and gas units and is owned by Genesis
Energy, which is one of the five big electricity-generating companies in New Zealand. We
investigate the role that Huntly plays in the electricity market, which companies would
benefit if Huntly's coal units are shut down, and which generation sources would be best
suited to making up the deficit of electricity supply.
From our analysis, it is apparent that the removal of units at Huntly increases the
strain on New Zealand's hydro network. Water becomes more valuable, and this impacts
the estimated distribution of operating surpluses for the five largest market participants.
If Huntly were to shut down entirely, electricity shortages would become more likely.
Hence, it is clear that new generation assets will be required in order to account for the
deficit in electricity supply if some or all of Huntly's units are shut down. We postulate
that geothermal and wind energy are best suited to replace Huntly's coal units, and that
the addition of all currently-consented geothermal and wind energy sources into the New
Zealand Electricity Market would significantly decrease the carbon emissions associated
with the generation of electricity.
Infinite-Horizon in Stochastic Dual Dynamic Programming (report) (literature survey)Shasa Foster ‒ December 18, 2018The New Zealand government aims for 100% of New Zealandâs electricity generation to come
from renewable sources by 2035. This objective is causing additional uncertainty around the
future of Huntly Power Stations' coal-fired units which already have intermittent use because
of their function as a 'peaker' during periods of extended low reservoir levels.
Determining the future of Huntly requires a model of the New Zealand Electricity Market
(NZEM). This project builds on previous research. Hydro-thermal scheduling models of the
NZEM such as JADE and DOASA have been used to research the value of Huntly in the NZEM
as well as future renewable generation mixes.
JADE and DOASA models are solved using the stochastic dual dynamic programming
algorithm (SDDP). An explicit assumption of SDDP is an exogenous, predefined terminal
marginal cost function. This assumption reduces the accuracy of these models and their results.
We extended the JADE model to an 'infinite-horizon' SDDP with an endogenous terminal
marginal cost function. Computational improvements reduced the run-time of the 'infinite-horizon'
SDDP from greater than 40 hours down to 30 minutes thus enabling accurate solutions
to determine the value of Huntly's coal-fired units and the future renewable generation mixes.
On reducing New Zealand's CO2 emissions (presentation)Andy Philpott and Tony Downward ‒ December 19, 2018