Import/Export monitoring + Energy Management Device trial
Grid import and PV export monitoring + Energy Management Device (EMD) trial A three phase research/innovation project funded by the EST in collaboration with Town & Country Housing Group
Phase 1 Town & Country Housing Group rolled out PV on some of their social housing in 2011. In line with best practice they used smart meters to track the PV performance and the kWh generation (for FiT payments). They also wanted to know how much of the PV generation was being used by their tenants and how much was being lost to the grid.
The EST funded the installation of smart meters into 32 properties to track grid import/export (along with the PV monitoring). From these three data streams it was possible to determine how much PV is being used, and what the overall electricity demand was, (PV-export = PV used, and, import + PV used = total demand).
Click on graphs to enlarge
After 8 months (March – Nov) of monitoring the aggregated total of the 32 properties the overall PV usage was approximately 30% – which is significantly lower than might have been expected according to industry and Government/agency estimates.
Of the 32 properties the results showed: Two exported over 90% of the PV (6.3% of properties) Five exported between 80%-90% (15.6% of properties) Eight exported between 70%-80% (25% of properties)
A strategy for getting more from the PV
These results were the driver for progressing the Energy Management Device (EMD) field trials which would be conducted in two further phases:
Phase 2: to find out if the devices work and the best place and way to fit them, and Phase 3: to analyze and confirm the practicability of a wider roll-out.
Phase 2: The aim was to explore a method of maximizing the use of PV generation by tenants by using EMDs to use up some of the otherwise exported PV generation to heat up hot water or electric block storage heaters.
There were 9 target properties in the trial. Three models of EMD were used – which were donated by the respective companies.
ImmerSUN (parent company 4eco Ltd) x 4: Installed Nov 2012 Genopter (parent company Meter Manager) x 4: Installed Nov 2012 Smart Power Controller (parent company Southdowns Solar) x 1: Installed June 2013
Six of the nine EMDs themselves were monitored with a smart meter which enabled us to confirm device behavior by comparing against grid import profiles.
Key analysis between 2012 and 2013:
PV generation: Down 2% (so levels of sunshine in both years was almost identical) Demand: dropped by 2% (also almost identical) Grid import: Down 102% PV exported: Down 20% PV used: Up 80%
The homes are all electric and have storage heaters. Some of the residents did not use their heating during the day and evening because it was too expensive.
Using the four streams of data it’s possible to assess the efficiency of the EMD.
Yellow = PV generation
Brown = Grid import
Blue = PV exported to the grid
Green = PV used in the property
Pink = Electricity through the EMD (mix of pre-set timer grid & PV harvest)
Click on graphs to enlarge image
Before: EMD installation:
Most of the PV is being exported (lost) to the grid – blue line.
The peak in the late evening (brown) is the Economy 7 timer coming on, however, this pre-set time did not correspond with the grid energy company’s E7 tariff time period – which meant the tenant was paying the premium rate price.
After: EMD installation:
PV is charging up the block storage heater during the morning.
Once the heater is hot then the PV is no longer needed and it is exported.
The peak in the early hours is the heater coming on for a pre-set time to ensure the house is warm when the resident gets up.
Before: 18th Nov – cloudy day.
Over-ride timer on the EMD kicks in to charge up the storage heater in the early hours of the morning.
It kicks in again in the late afternoon because on a cloudy day the EMD cannot harvest any electricity.
After: 19th Nov – sunny day.
Timer kicks in in at night to ensure warmth in the morning.
PV charges up heater throughout the day so the timer boost is not needed in the afternoon and the resident doesn’t need to use a plug-in backup heater to stay warm.
Phase 3: Has just got under way. EMDs will be used in 6 target properties to confirm the viability of using Energy Management Devices as an alternative way of providing heating.
The overall aim is to understand enough after the field trials to roll-out EMDs without having to micro project manage the process or install monitoring meters.
Energence specialises in the careful project management of complicated research projects as well as the more straight forward stuff like Feed in Tariff and Renewable Heat Incentive monitoring.