Thermodynamic panel test

Thermodynamic panel under test at Narec Distributed EnergyThermodynamic panel under test at Narec Distributed Energy

Narec Distributed Energy carried out the first UK independent test of a solar thermodynamic panel at their renewable heating test centre in Blyth.

If you would like more information on what a Thermodynamic Panel is, please go to our Thermodynamic Panel Technology Page.

Overview

The system was installed on the 11th December 2013. As with any new project, teething difficulties were experienced and the test start was further delayed by the annual building shut-down over Christmas. However, we have valid and reliable data from 10th January 2014 onwards and a complete data set from 17th January 2014 to the 31st July 2014. This summary presents the data available from the test so far.

Thermodynamic Panel Test Details

System: Hyrax Aqua

Tapping Cycle: Tapping Cycle No.2 from EN 13203-2

Period: December 2013 – July 2014

Laboratory: Narec Distributed Energy Thermal Testing Lab

Parameters measured Unit
Thermal energy produced to hot water Wh
Electricity consumed Wh
Total solar irradiance Wh
Average external ambient temperature °C
Average cold feed temperature °C
Average store room temperature °C
Average hot water supply temperature °C
Monthly totals of above °C and kWh

Coefficient of Performance (COP)

The COP is obtained by dividing the daily hot water energy delivered by the electricity consumed, in line with practice in the heat pump industry. This method does not take account of the tank losses, which were investigated by operating with the immersion heater only for the period 16:00 on Friday 24th January to 9:45 on Monday 27th January.

Narec Distributed Energy - Independent Thermodynamic Panel Test - January 2014 dataFigure 1: January 2014 data
Blue row = double output of water due to testing
Grey row = testing of system with purely the immersion
Narec Distributed Energy - Independent Thermodynamic Panel Test - February 2014 dataFigure 2: February 2014 data
Narec Distributed Energy - Independent Thermodynamic Panel Test - March 2014 dataFigure 3: March 2014 data (Note, scale changed)
Narec Distributed Energy - Independent Thermodynamic Panel Test - April 2014 data - graphFigure 4: April 2014 data
Narec Distributed Energy - Independent Thermodynamic Panel Test - May 2014 data - graphFigure 5: May 2014 data
Narec Distributed Energy - Independent Thermodynamic Panel Test - June 2014 data - graphFigure 6: June 2014 data
Narec Distributed Energy - Independent Thermodynamic Panel Test - July 2014 graphFigure 7: July 2014 data
Orange row = testing under tapping cycle No.3

January: The average COP over the compressor only period is 1.02, falling to 0.67 using the immersion heater. The COP rises to 1.68 on Jan 22nd due to an increased hot water demand (approx double) when conducting verification of the tap cycle control system; suggesting unit performance improves when subjected to higher loading. The COP also rises to 1.92 following the immersion heating (due to previously stored heat from the immersion heater resulting in tank temperature greater than the set point of 55°C) so should be disregarded as non-representative of normal use.

February: The system ran continuously throughout February, with an average COP of 1.07, with a maximum of 1.50.

March: Time switch placed on system to ensure that it takes advantage of solar irradiance more. Average COP of 1.34, with a maximum of 1.89. Taking account of tank loses this had a maximum of 2.64.

April: Average COP of 1.39, with an maximum of 1.7. Taking into account the tank loses this gave a maximum of 2.38. This decrease is not unexpected, as the average daily irradiance in April was 2206Wh, as opposed to 2743Wh in March.

May: A 23.9% increase in irradiance from April led to a 9.7% improvement in the COP. The average COP was 1.5 (2.1 taking account tank losses). Peak COP with tank losses taken into account was 2.51.

June: There was a 2.4% reduction in solar irradiance , whilst the outdoor ambient temperature was up by 19% to 17°C. The COP increased by 4.4% , with an average (including tank losses) of 2.19. The average electricity use was down by 4.8%, at 3.66kWh per day

July: The COP (when including the tank loses) breaks the 2.5 barrier, which is of significant relevance to heat pumps due to the European Commission  Renewable Energy Directive. 9 days of testing were also carried out using Tapping Cycle No.3, to understand the impact of a greater water demand on the COP, no real difference was found, in contradiction to the COP findings on the 22nd Jan.

Many people are comparing these COPs to those from air source heat pumps, please see our FAQ page to understand why this is an unfair comparison.

Tank losses

Tank losses are a feature of stored water systems and 2.5kWh per day is not uncommon for a good performance cylinder.  An analysis was done of the early hours immersion heated period (where the energy supplied can reasonably be assumed to be only overcoming tank heat loss) for the 6 hour period 00:00 to 06:00 averages 572Wh over the 3 mornings, hence the predicted 24 hr loss is 2.289kWh; slightly less than a typical high performance cylinder under CHeSS*. If this is applied to the data in Table 1, the average COP for the period rises to 1.43.

Data

Thermodynamic Panel data from independent testTable 1: Thermodynamic panel test data for January 2014: Test by Narec DE
Thermodynamic Panel data from independent test - February 2014Table 2: Thermodynamic panel test data for February 2014: Test by Narec DE
Thermodynamic panel test data for March 2014: Test by Narec DETable 3: Thermodynamic panel test data for March 2014: Test by Narec DE
Narec Distributed Energy - Independent Thermodynamic Panel Test - April 2014 dataTable 4: Thermodynamic panel test data for April 2014: Test by Narec DE
Narec Distributed Energy - Independent Thermodynamic Panel Test - May 2014 dataTable 5: Thermodynamic panel test data for May 2014: Test by Narec DE
Narec Distributed Energy - Independent Thermodynamic Panel Test - June 2014 dataTable 6: Thermodynamic panel test data for June 2014: Test by Narec DE
Narec Distributed Energy - Independent Thermodynamic Panel Test - July 2014 dataTable 6: Thermodynamic panel test data for July 2014: Test by Narec DE
Tout °C = External air temp
Tamb °C = Ambient temperature of laboratory
Ttank °C = Temperature of water in tank
Irrad Wh = Irradiance in plain of panel
Eelec Wh = Electricity consumed
COP = Coefficient of performance
COP inc tank loss = Coefficient of performance without tank loses
Blue row = double output of water due to testing
Grey row = testing of system with purely the immersion
Orange row = testing using Tapping Cyle No.3

Enquiries

This data is provided in good faith and we hope you understand we have limited resource to answer queries related to it. However, we will always endeavour to respond to reasonable requests.

Please also look to our Thermodynamic Panel Test Frequently Asked Questions page for more information.

[*] Energy Savings Trust, CE51 “Central Heating Equipment Specifications (CHeSS)”, 2008