3. Methodology
The report1Availabilities and Costs of Renewable Sources of Energy for Generating Electricity and Heat included analysis of the availability and cost of all publicly known hydro opportunities. The costs were updated to 2002 values and the authors used their judgement to establish the level of confidence of each opportunity proceeding. The data was aggregated to provide information on confidence levels and costs at both regional and national level. Information on specific projects or catchments was not included.
The opportunities in the 2002 report having high or medium confidence levels of proceeding in the next 20 years have been reanalysed for this report. The historically based information has been updated and adjusted to take account of the community's current attitudes and aspirations that could be a determining factor when resource consent applications are received.
Other opportunities considered of possible future interest that were not included in the 2002 high/medium categories have been re-evaluated and included in this report where appropriate. It should be noted that this is very subjective and dependant on, among other things, the authors' assessment of future community attitudes towards hydro projects.
The catchment numbers (e.g. Catchment #2, Waikato) are taken from project maps (one North Island, one South Island) supplied by the Ministry of Economic Development for this purpose. In a few cases where catchments are very small, and similar to adjacent catchments the number selected may be that of an adjacent or nearby catchment.
A basis of the authors' assessment is that future hydro projects will:
- Tend to not involve river impoundment but will be out of river modular canal type designs,
- Be smaller than traditional hydro projects in NZ,
- Involve shared use of extracted water for irrigation or community water supply,
- Have residual river flows as a determining factor for the level of generation, and
- Be integrated into the needs of other water users.
Hydro electricity projects which involve a degree of impoundment are in the future likely to be used more for peak electricity generation and be linked to wind energy projects where the water storage acts as a form of battery for the wind energy. The two energy forms having their operation integrated.
The report is constrained in that there are a number of opportunities being progressed by interested parties (usually developers or potential developers etc) that the authors are not aware of. Also some information is confidential to specific developers and as it is not in the public arena has not been able to be included in this report. While not a large number, nor significant in the overall context of the total MW / GWh figures, they nevertheless represent a significant proportion of likely near-term developments simply because they are the current focus of potential developer activity.
In addition a number of previously identified opportunities were discarded at an early stage of investigation as they were not perceived to be economic, or that there were environmental issues that were perceived as difficult to resolve, or provide too much risk. There is generally little information in the public arena on these projects. The authors have included appropriate ones under "Other Opportunities" for each region.
There is also the issue of access. It is known that some opportunities exist but the asking price for access to the resource is too "high" in that there are other competing land or water uses.
In addition most of the publicly available information is from projects and investigations that are now several decades old. The investigations were undertaken based on assumptions that may no longer be applicable. Where the assumptions are known by the authors adjustments to the information have been made. There will however be a number of projects where critical assumptions can no longer be identified. In general, such projects have been included "as is".
In recent years there has been little investigation of hydro opportunities because;
- There has been strong anti-hydro community attitudes.
- Hydro investigations are very expensive, and take a long time to complete, with little confidence that resource consents will be able to be obtained.
- Hydro projects potentially can affect large numbers of landowners and nearby communities all of whom require extensive and expensive consultation.
- Water impoundment can involve a large land use change.
- To prepare properly for resource consent applications is very costly.
As a result some of the data available for this report are very dated which will affect the confidence of the information. The date of information sources for each of the projects is listed.
The hydro potential in catchments is affected by topography, soil geology, river flows, and other interests associated with a particular water body e.g. fishing, canoeing. Some rivers are very "flashy" with the result that either storage is ideal, or extensive construction features are required for rare flash events.
Information on flow is one of the significant uncertainties facing a developer. A good long-term (a large number of years) record of flow data is essential if the resource is to be well understood. This information has been and is continuing to be collected but is not necessarily freely or readily available to the public in a form that can provide the appropriate information.
Variations in flow, particularly if they are consistently below the assumed mean flow will have an adverse effect on the return an investor/developer will receive for the project. That, along with civil engineering uncertainties for foundations are two of the most significant factors that must be assessed and understood before construction is committed to.
To take account of these issues the authors have included commentary on the potential opportunities in each region that should not be lost sight of just because there is little information currently available. Indications of potential are based on the principle that where there is flow and "head"2 there is an opportunity. Changes in technology, conceptual design thinking and relative economics over the next 20 years will result in some currently uninvestigated opportunities becoming relevant for investment.
Opportunities excluded from consideration are those in National Parks. Where a Water Conservation Order covers a river with hydro potential these opportunities are included for consideration as there is a mechanism whereby Water Conservation Orders (as Regulations) can be modified. Similarly for those regional rules that superseded Local Conservation notices. The particular effects of these on specific projects has not been fully assessed as this is outside the scope of this study. Opportunities impinging on the Conservation Estate have been included where there is a possibility that the opportunity could proceed. Many opportunities in the Conservation Estate have been excluded because of the high potential adverse effects.
The Chatham Islands and Stewart Islands have not been included in the scope of this investigation as they are isolated from the grid at either the national grid or local network level.
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