HMG Visit to Town Mill, Alresford
Eleanor Yates, Ivor New , Peter Mobbs photographs - Keith Andrews
On October 21
members visited this site to see a newly installed Hydropower facility.
The river Arle comes from
the Old Alresford pond, which was originally a fish pond for the
Bishop's Palace at Bishop's Sutton. Town Mill on the Arle was rebuilt
in the 1890s on the site of earlier mills dating back to the 14C. This
building was a roller mill using two turbines in the river below the
building but in the 1920s, it stopped grinding flour and only sold
animal feeds until the rollers were removed in 1939. The rest of the
milling equipment was sold in 1969 and the building used for storage and
later a laundry and a toy factory before being turned into two
residences. The turbines are thought to remain in situ in the old
turbine room under the kitchen’s concrete floor.
In 2008, our host David
Fitzgerald started the long drawn out planning procedure necessary to
replace the Victorian turbines with a modern state of the art Hydropower
unit. Some HMG members had looked at early plans for this installation
David outlined some details
of the process. This involved meetings with the Design Consultant,
Environment Agency, the Council and the Electricity Board. It was
essential to obtain reliable values for the water flow rate and
available head so a flow meter was installed and monitored over a period
of several months. This established that there is an average flow
of about 0.7 cubic metres/sec. A fall of 3 metre is available.
A decision was made to
install a "cross flow turbine" drawing up to 0.6 cubic metres/sec, which
can generate up to 10 kW electric power. It was estimated that 75% of
this output would be exported to the National Grid.
The EA were worried that
the penstock would act as a barrier to fish, so provision was made to
install a fish ladder with 18" steps that incorporate a small pool
behind each step. This would allow the fish to recover before their
next leap! The ladder has a minimum design flow rate of 80 litres/sec.
Winchester City Council and
New Alresford Town Parish Council were very supportive of the proposed
development although there were concerns about noise from the turbine
and alterations to the weirs. Local concerns included the impact on
wildlife, water-flow, possible flooding and that little electricity
would be generated. All these worries were satisfied before planning
permission was granted.