INTRO:
This latest set of studies, on the optimisation of energy efficiency of ceiling mounted IR heating panels, took place over the period mid-January 2022 to late March 2022. The studies were in the same 70m3 L shaped office as was used for Case Study No 1 (see).2 IR panel heaters were positioned (ceiling mounted, 1 in each ‘leg’ of the L shaped room) to give relatively uniform heating across the full room. Combined, these equated to 20W/ cubic metre installed heating capacity – which itself is very appreciably below usually recommended levels, particularly given the age & construction of the building and the relatively modest insulation levels involved (again, see CaseStudy 1).
In addition, throughout these trials, a constant level of fresh air ventilation was continuously introduced into the room, (as an anti-covid precautionary measure, x-ref Case Study 4 for further background), by wedging open the 2doors – respectively towards each end of the room (30mm gap for each), with the replacement air coming from totally unheated, open areas of the premises (see below).
The trials also used our exciting new control technology development. When used in conjunction with our unique IR panels, these delivered really frugal levels of energy consumption (detailed below).
The result, room comfort heating - even in a relatively poorly insulated 1950's building - using only around 0.5kwh/h to heat a 70m3, L-shaped office, despite constant air ventilation throughout the working day.
UNIQUE USER BENEFITS OF 2DHEAT IR PANELS
1. COMPACTNESS & VERY RAPID HEAT-UP FROM COLD
- Our patent-pending new resistor technology, with unparalleled watts density operating levels, allow not only compact & lightweight panel sizes – 595x595mm for a full range of power ratings (300W - 1800W) but also their instantaneous initial heat-up profile.
- Within only 1-2 seconds from 'cold' switch-on, they deliver energy spikes some 45-50% higher than their nominal 'stable state' power rating. (eg: 1040w from a 700w rated panel; 880w from a 600w rated panel).
- Because of their strongly PTC nature, these then asymptotically 'decay' to their nominal power ratings, over a period of ~40mins. But this very sudden burst of energy gives the initial, very reassuring, room heating effect, arising uniquely from the IR energy emitted - there being very limited warming of the room infrastructure surfaces (particularly walls) or of the air during this early stage.
- This rapid heat-up performance is, we believe, unique to our IR panels as is the ability to provide a full wattage range onto a 595x595mm standard panel size. This latter feature vastly simplifies installation requirements, obviating installation errors when physically different panel sizes are involved.
2. EASY 'DIAL-DOWN' (TO ACHIEVE OPTIMUM ECONOMY)
- An 'easy dial down' feature, (at the moment, progressing through the commercial prototype stage),then comes into play. This reduces the power rating of the panel so as to give optimal economic performance whilst anticipating the room comfort aspects desired. This typically can be achieved using energy input levels of 1/2 or even 1/3 of the notionally designed energy input requirements for the type& size of room in question.
- To illustrate this, a trial run on Thursday 17th March 2022 delivered a very reassuring ASHRAE comfort factor of +0.5 (see footnote for definition), even whilst the heated surface temperatures (especially the walls) were recording an average of17oC (spread 15.5o-18oC),with air temperatures lagging behind those levels - average 15.5oC (spread 15o-16.5oC).
- Unheated areas of the building - with which the test office was continuously linked (via 2 open-doors 'trickle' venting arrangement as an anti-Covid precaution) averaged 11.2oC air temperature in the work-shop area ( spread 9.5o-13oC),and 10.6oC (spread 9.3o to 12.3oC) in the building entrance lobby.
TRIAL DETAILS
In these trials, 2 separate heater panels were ceiling mounted, one a nominal 750W the other nominal 600W, based on (together) providing ~20W/M3 energy input into the room. Each was fitted with an independent 'dial-down' capability. It should be noted that the 1350W combined installed power rating is around only half of the "considered wisdom" energy input level required for this sizeof room in a relatively poorly rated U value (estimated at 2.3-2.5W/m2/K, albeit relatively well sheltered from winds, etc, by its location within a larger factory unit).
During the initial 'energy-burst' period (2-3 seconds duration only) the energy delivered into the room was an instantaneous1880W falling slowly to the nominal 1350W level. Later in the day 2 separate dial-down adjustments were made, the first mid-morning (to ~680W combined), followed by a 2nd (early p.m.) to a combined ~416W combined).
ENERGY USAGE PERFORMANCE
Resultant energy usage across the full working day (8.25 hours) was 0.556 kwh/h with an ASHRAE comfort factor assessment of between ‘-0.5' (initial) to '+0.5' being recorded across the full working day.
This narrow target spread of comfort factor is the OPTIMUM target comfort zone for best energy efficiency. This calculation includes the all-important initial energy surge of ~1808w which is essential to quickly take the cold early ASHRAE rating from '-1.0' to a tolerable initial comfort level of '-0.5'.
CONTRAST WITH THE TRIAL OF TUESDAY 15/03/2022
A very similar trial was conducted 2 days earlier during which the same heaters, same locations, etc were used. Only the dial-down timings and degree of adjustments varied - the initial dial-down occurred 1 hour later on the Tuesday (compared with the above Thursday run) and to a combined level of ~743W (vs ~680W above), with the2nd dial down still occurring at 2:00pm but, again to a higher adjusted level of ~525W (vs ~416W above). These higher energy levels(during the Tuesday run) generated both quicker and higher surface temperatures being achieved ( 16.5o-19oC vs 15.5o-18oC),with air temperatures achieved being only slightly higher (15.5o-16.5oCvs 15o-16.5o C) but with ASHRAE comfort level assessments recorded, reaching '+1.0' at peak (vs only '+0.5' on theThursday). However, these combined changes increased the overall energy usage to an average of 0.748 kwh/h across the full working day - i.e. 35% inferior energy efficiency delivered compared with the trial of 17/03/2022.
Earlier still trials (Friday 11/03/2022 for example) resulted in even poorer overall energy efficiency levels (1.208 kwh/h)across the working day because the first dial down wasn't introduced until lunchtime (13:30 hrs), when only 1 of the elements was dialed-down (from 760w to 510w) with the dial-down of the 2nd panel only being done at 15:30 hrs (660w to 475w). By that time the room had simply become too hot, having achieved a comfort level of at least '+1.0'across a 3 hour period, during which air temperatures attained a steady 17.7-18.0oC with wall temperatures recording 20oC. Even though all heating was shut-off at 16:00hrs, the comfort factor was still at'+0.5' at 17:30 hrs.
Conclusion, for best energy efficiency results, never let wall temperatures remotely achieve 20degC - moderate the energy input levels well before that point.
COVID VENTILATION MEASURES
As a final PS type comment, it should be remembered that the whole series of tests used to generate the above data were run with constant ("anti-covid") 'air circulation' across the 70m3 room - achieved by leaving 2 doors, one located at each end of the room, constantly ~30mms 'ajar', venting respectively onto the (unheated) lobby into our building and onto a large unheated workshop area, the ambient temperatures of which were also recorded and are shown on the respective 'graphics', an appreciably more severe test challenge than using either a fully sealed room or even a passiv-haus situation.
KEY CONCLUSIONS FROM THIS STUDY
A very good level of 'radiant comfort factor' is perfectly achievable with a room air temperature of between 15O-16OC.
Air temperatures of above 17OC merely represent where excessive energy wastage is being incurred when using IR heating.
The moral? Never let wall or air temperatures reach 20degC when using IR heating!! Otherwise economic heating won’t be achieved….
AND BACKED BY INDEPENDENT DATA
In collaboration with a major housing association, 2 of our panel heaters have been successfully installed (since October 2021) - in a real-life usage situation in a 2 room apartment in a 1960's tower block in Northern England. This property had proven to be ‘impossible’ to economically heat using conventional heating systems.
We have been remotely logging (with the landlord's & tenant's consent) basic data such as usage pattern, switch on-off times, temperatures attained. The 5 months worth of data has been analysed, but the accompanying real-time energy data & costs are still awaited.
What we do have is very positive feedback from the tenant that this has been the first time that he has been comfortably heated, and at affordable cost.
These 2 installed panels (respectively 700W and 800W) were equipped only with basic on-off controls and a wired-in thermostat. The 'dial-down' capability was not installed because of its development status. The usage data showed that initially the tenant turned 'on' and left on the panels, but quickly attuned to optimising economy in use, using just the simple on/off switch for that purpose. The housing association concerned sees this as an extremely positive development, which they are now looking to expand further across their property estate.
FOOTNOTE - ASHRAE FACTOR definition used for scoring:
+1.0 = Very comfortable! In fact too comfortable for COP26 delivery!!
+0.5 = Comfortably warm.
0 = The"Goldilocks" point - neither hot, nor cold.
-0.5 = OK even though 'a bit on the cool side'.
-1.0 = Too chilly for desk working comfort.