The Esk Hydro Project
The Esk Hydro Project is located in the headwater of the Esk River, north of Napier. The scheme consists of two high head stations developing a combined output of 3.8 MW and an estimated 15.2 GWhrs per annum, (up to 2000 homes).
The scheme consists of two separate stations drawing on separate tributaries of the Esk River. The stations do not cascade and as such the design of each can be optimised separately. The stations share a common transmission system and land access agreements.
This is the larger of the two stations with a design output range of 2.0 to 2.4 MW. The station has a gross head of over 340m and a maximum consented flow of up to 1.0 cumecs. It will draw water from a low overflow weir via a control gate and abstraction chamber, whilst releasing a small residual flow (required by consent) back to the stream. A sediment removal facility will be installed at the beginning of the penstock to remove particles > 0.5mm and thereby maximise the wear life of the Pelton turbine buckets.
The conveyance is almost entirely penstock and some 2.4 km in length. The initial section will be relatively low pressure and will utilise GRP while the lower high pressure section will utilise steel pipe. The powerhouse is located by the stream and will consist of a relatively simple steel clad shed. The turbine will be a locally designed and manufactured vertical pelton turbine by HydroWorks and Allied Engineering Ltd.
Storage is currently not consented for the Rimu component of the scheme. However negotiations are commencing with the landowner to secure agreements to pursue a Resource Consent to install a small 4,000m3 (4 hrs storage) pond. Such an enhancement will add value to the scheme if we can get it approved.
This is the smaller of the two stations with a design output range of 1.0 to 1.4MW. The station has a gross head of over 140m and a maximum consented flow of up to 1.2 cumecs. It draws from low overflow weirs on two small streams via sediment removal canal and control gates that then flow into the 900m long penstock. A small residual flow (required by consent) will be continuously released from the weirs back to the streams.
The conveyance is predominantly penstock (900m in length). The initial section will be relatively low pressure and will utilise GRP while the remaining high pressure section will utilise steel pipe. The powerhouse is located by the stream and will consist of a relatively simple steel clad shed. The slopes of the gorge in the vicinity of the powerhouse are steep with some land instability and continuous ground seepage. These risks will be controlled and managed through the installation of drainage channels and locating the powerhouse away from the base of steep slopes.
The turbine will be a slightly smaller vertical Pelton than the Rimu turbine and it will also be locally designed and manufactured by HydroWorks and Allied Engineering Ltd.
Storage is consented and will be provided by a 4,000m3 canal which provides daily regulation and 4 hours peak output during peak demand and price periods