Consultants differ over wind power
While Australian based consultants KEMA have recently recommended a renewable energy scenario based primarily around wind power, ( 53% wind power/ 28% solar power/10% Waste to energy -bio-mass) to government for Rarotonga, another energy consultant, Gerhard Zieroth’s recommendation to Te Aponga Uira in 2011 presents a scenario based primarily around solar power.
This is what Zieroth says in his Executive Summary:
“This report summarizes the results of an analysis undertaken in the framework of a consultancy on
behalf of Te Aponga, Cook Islands. The objective of the analysis was to test the feasibility of the
renewable energy targets formulated by the Cook Island Government and lay out a strategy for
TAU that would maximize renewable energy contribution in the Rarotonga system without
undermining the financial viability of TAU and without imposing tariff increases on Rarotonga’s
power consumers. The targets require 50% of power in Cook Islands be generated from
renewable sources by end of 2015 and 100% by end of 2020.
These targets are achievable, but only if imported biodiesel becomes part of the generation mix.
Relying on the three locally available renewable energy sources solar, wind and waste would require a massive investment in grid upgrading and storage. The following table summarizes the investment requirements for two scenarios: A scenario that aims at 100 % local RE and a scenario
that optimizes RE investment by avoiding major grid upgrades and storage investment. The
second scenario is based on a realistic investment sequence that would ramp the contribution of
local RE sources to 50% by 2020 and fill the gap with imported biodiesel. While biodiesel will be
25% more expensive than regular diesel, total cost of this solution would be significantly lower than
the scenario that provides 100 % power from local, renewable energy sources.”
Under Zieroth’s scenario for Rarotonga, solar takes precedence over wind and while he queries the application of waste to energy (bio-mass) technology, he also includes imported bio-diesel in his mix as an option for achieving the renewable energy target.
For TAU to achieve 100% renewable energy by 2020, Zieroth has taken the approach of looking at a supply driven expansion plan instead of a demand driven expansion plan. In other words the Rarotonga power system which has been designed to supply a demand of approximately 5 MW would have to be turned into a system that has to handle up to 20 MW of renewable energy supply, most of which will have to be stored.
Zieroth has considered storage options and costs both to TAU and the consumer relating to installation and upkeep. He has also considered constraints like land availability, terrain and current and future weather patterns.
His recommended model is based on power generation taking all factors into consideration.
Technology installed capacity kW Remarks
Large solar 15,000 Site identification and
feasibility study needed,
Medium wind 900 Site identification and
feasibility study needed.
Waste to energy 500 Feasibility study required.
Net metering 1,000 Assumes expansion of
programme with
10kW cap.
Zieroth says 50% renewable energy could be achieved by reducing the solar generation to 5,000kW and retaining TAU’s diesel generation.
Alternatively, 100% is achievable if TAU uses bio-diesel. While bio-diesel would cost 25% more than diesel, it saves costs in the long run because less investment is needed in storage systems.
Zieroth’s recommendation? He recommends that Government and TAU agree on a 50% RE plus biodiesel solution and start preparatory activities immediately. -Charles Pitt

Herald Issue 608 21 March
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