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SoLa Bristol

DurationDecember 2011 - January 2016
  • South West

Project description

What is BRISTOL?

"B.R.I.S.T.O.L." was the Buildings, Renewables and Integrated Storage, with Tariffs to Overcome network Limitations project.

Our customers’ energy demands are continually evolving; the design and operation of the Low Voltage (LV) distribution network needs to develop at the same rate. The introduction of Low Carbon Technologies is increasingly stressing the Low Voltage distribution network, in some areas preventing customers from connecting either generation or demand without conventional reinforcement.

The project tested the following Hypothesis:

1. Should new Low Carbon Technologies increase distribution network peaks and cause thermal overloads; then battery storage, demand response and DC networks could be an efficient solution, this is because conventional network reinforcement for short thermal overloads may not the most efficient use of customers’ money.

2. If DC networks in properties could be used to reduce network harmonics, phase distortion and improve voltage control then their use may be vital in the connection of Low Carbon Technologies. This is because the safe, efficient operation of distribution networks is reliant on the power quality and voltage being within statutory limits.

3. If DNOs and customers could share battery storage on DC networks with a variable tariff, then the mutual benefits may make battery storage financially viable. This is because battery storage could be a shared asset or sold to customers.

    • Lower energy bills
      • Better control of energy; a Smart Tariff rewarded customers for reducing their peak energy demand, passing on the cost savings.
    • Improved energy efficiency
      • Increased efficiency supplied DC equipment using the DC network instead of more inefficient AC/DC converters
    • Quicker and cheaper connection of Low Carbon Technologies
      • Traditional network reinforcement can be prohibitively expensive and require significant scheduling; the BRISTOL solution was one that could be implemented much faster.
  • 30 homes had 2KW of battery storage installed in their lofts along with PV Solar panels. The PV Panels were directly connected to the battery to store solar energy for use when the sun was not shining. In addition to this each home had a DC micro grid installed, that also ran from the battery, providing all the lighting and USB charge points. Each home was also connected to the local electricity network, so that excess stored energy could be exported to the grid at peak times.

    Solar batteries in a loft

    5 Commercial building, including Schools across Bristol had 8KW of battery storage installed, along with a DC micro grid for their IT suite that ran the lighting and IT equipment. This was also linked to the local electricity network to enable export at peak times.

    Lights on ceiling

    All relevant data was captured to enable analysis on the benefits to customers and the electricity network, along with the effect of the systems on power quality.


  • Below are some explanations of terminology relating to So La Bristol:


    Alternating Current comes into your house and is also known as mains electricity.  It is converted to DC using special plugs or power bricks to run computers, mobile phones, mp3 players and other DC appliances. 

    Battery storage

    The special batteries that will be stored in your loft. They will power your lights and other gadgets connected to the DC network when your solar panels aren’t generating electricity.

    CFL and LED Lighting

    Compact Florescent Lights (CFL) or Light Emitting Diode (LED) light bulbs are energy saving light bulbs that are powered by DC.


    A box that can change electricity from AC and DC and DC to AC within your home. It will be stored in the loft with the batteries and will top up your batteries if your solar panels don’t generate enough electricity during the winter months. 


    Direct Current is used to power a large number of applications around your home and will be used more and more in the future.  Very efficient lighting, mobile phones, computers and anything that is battery powered already uses Direct Current. 

    DC network

    The wires in your house that will power your lights. These wires will have low voltage DC power instead of AC power and will power all your DC appliances.

    Home Energy Monitor

    A box that will monitor the solar panels, batteries and the DC network. It will feed the information to your tablet PC to display how much electricity is being generated by the solar PV, how much energy is in the battery storage and how much you have saved with the variable tariff (see 'Frequently Asked Questions').

    Smart Energy Hub

    A box that you can plug your tablet PC, mobile phone, mp3 players and other DC equipment into and charge them.

    Solar PV

    Solar photovoltaic. A number of panels connected together on your roof that can convert the sun’s rays into electricity. Often referred to as solar panels.

    Tablet PC

    A mobile computer with a touch screen. You will be able to keep this at the end of the project.

  • Obtaining good quality data was a key factor of success for SoLa Bristol. The design phase was predicated on the achievement of a robust, but viable, design that could deliver the requirement in the timescales. We believe that this was a considerable achievement given the complexity of the requirement. Therefore to get good data we see as a particularly strong message for SoLa Bristol. 

    The analysis of the data has been another challenge because of the volume of data and the amount of analysis required in order to test the hypothesis. However, this has been completed and the full results are detailed within the Final Report. 

    The high level results from the analysis were as follows: 

    • Network Benefits - there were some observed benefits that were seen from the project. Further work is required, however indications are that although the penetration of battery and PV was relatively low in the trial network and there was some demand uncertainty, the network demand change was not reflected in the measured data and therefore the corresponding network investment deferral was small. When the penetration level is theoretically increased, the network investment deferral is increased to thousands of pounds. However, clearly this is not material enough to justify the considerable investment. 

    • Domestic Customer Benefits - The average saving of the 11 houses on substation 3 was £52.10 during the trial, and the average saving per month equated to £7.43. 

    • Commercial Customer Benefits - In the schools, only the battery was taken into account for calculating benefit. The schools implemented the new EMS strategies at the end of November 2014. Therefore, the school’s ToU benefit was calculated from December 2014 through to May 2015. The six months benefit received by the school was c. 0.9%. As the weekday and weekend EMS strategies were different, the benefit of weekdays and weekends was consequently different. The average benefit received per month was £5.83.

    The full analysis can be found within the Final Report

    Given these results, it is absolutely clear that change is needed and we discuss more on this later in this report.