The EMMA units deployed in NTVV have a control algorithm especially configured for this project to adjust the amount of PV energy exported on to the network by diverting excess amounts to a conventional hot water storage tank via the customers existing immersion heater. The units, adjusted for this project:

  • use a learning model of the maximum output from the PV system to calculate a generation profile for the site. The control algorithm takes in to account the time of year, the size of the PV system and the time of peak output.
  • consider the customer’s expected thermal storage needs (hot water tank), which are expected to be between 3kWh to 6kWh per day, subject to PV generation and daily usage.

Based upon the above criteria, the unit calculates how much energy can be diverted off the peak export to the supply, typically for a household with a PV capacity of 5kWh this is expected to be 1kW. Therefore when PV production meets expectations i.e. when there is sufficient daily light, the customer will receive a regular, expected, amount of hot water, whilst simultaneously diverting the peak export power to the LV network.
The installation, operation and location(s) of the units are recorded within SDRC Evidence Report 9.4(b), as submitted in March 2014. Analysis of hot thermal storage requires energy data to be periodically down loaded from the individual units to understand the effects of the installed units on peak PV generation, within the property and on the LV network.
This report was established to acknowledge the clear focus given to the optimisation of hot thermal storage, both in terms of quantity and location. In particular, the project has sought to:

  • deploy the required hot thermal storage hardware in a cost effective manner, hence providing the maximum ultimate benefit to customers
  • review the data from the units, during re-visits, to confirm satisfactory ongoing operation and that the unit continues to meet the participant¡¦s expectations
  • review the periodically down loaded data from the units to understand the effects on peak PV generation, and how this may affect future deployments
  • draw on in depth analysis of the electronic characteristics of the EMMA 3G design, and in partnership with Imperial College (London)1 via a separately funded innovation project.
  • identify optimum locations for the use of these units in addressing LV network constraints which may result from significant PV generation.