Solar Heat Energy Demonstrator

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To Do:

  • Review designs and calculate loads
  • Produce schematic of proposed design
  • Detailed design of pipework and equipment

Aims

The aim of the project is two-fold.

  • Provide better heating for the building using low carbon heat, bringing the building up to a suitable level of heating to be passed on to the next occupants.
  • Conduct detailed tests to work out the best practices and installation choices, to maximise in-use efficiency of CO2 heat pump technology, and work out it's place in the renewables landscape for the future.

Requirements

Following initial site meetings the following requirements have been set:

  • Installation of CO2 air source heat pump(s)
  • Low use domestic hot water
  • Central heating to 10 office spaces
  • Office spaces to be fitted with a selection of heat emitter types
  • System to be flexible enough to allow different heating strategies to be tested
  • System must be of a standard to be handed over to the next building occupants
  • System must allow for the optional use of fan convectors as final stage to heat the main area and lower return temperatures
  • System to be provide real-time operational data and allow details adjustment of settings and controls logic

Documents

Proposed SHED Upgrading Works - first floor layout.pdf Proposed Occupancy Office Layout.pdf LE 155 0 ExistingShed-Ground.pdf LE 155 0 Existing SHED-First (1).pdf P2 04 Existing South & West Elevations (2).pdf P2 03 Existing North & East Elevations (2).pdf

Design Points

The following points have been considered.



  • QAVH connection to buffer store. This arrangement is used to draw heat from the cold part of the buffer for defrost protection.

  • Setting 121 decides secondary control is enabled. We do not need secondary control so it can be left in default setting (off).

  • Trace heating (electrical tape) is used to prevent pipework from freezing as a matter of last resort if the circulation pump should fail for defrosting. We will tie control over this into system.

  • Because of the need for (1) the heat pump defrost circuit to go through the store, and (2) the stability of the output from the heat pump is unknown and could do with some buffering via the top of the buffer store, it will be prudent to fit buffer stores with internal diffuser plates to create chambers to contain turbulence, and maintain stratification. NOTE: When only 1 buffer is to be used, top and bottom plates in same store

  • This table shows water quality requirements for the heat pump, and also for a secondary side (not used in SHED). It is important that regular tests are made to ensure this is met. It is also advisable to install water filtration equipment that can maintain these parameters with as little maintenance as possible. Remote monitoring on each of these would be nice.

System Schematic

  • Double-click in the diagram background in order to add a new node there.
  • Add ports to a selected node by clicking the above buttons or by using the context menu.
  • Draw links between ports by dragging between ports.
  • Right-click on a port to bring up menu.


Heating Schematic


Controls Strategy

Heat Pump Control

  • Control of the CO2 heat pump is based on recovery of the associated 500 litre buffer store.
  • Temperature sensors in the buffer store at different positions provide signals to the heat pump controls.
  • The heat pump will start reheating the buffer when there is a set volume of water ready to reheat and continue until the buffer is fully heated
  • The temperature the heat pump heats water to is set using an external control signal, and will be driven by required temperatures to deliver hot water and central heating, between 60C and 85C.
  • Temperature requirements will be calculated from external air temperatures.
  • The power output of the heat pump may also be externally controlled.
  • In order to minimise the number of firing cycles per day, the power will be modulated in order to achieve a steady state where possible, reverting to batch loading where loads are lower than minimum heat pump output.
  • The COP off the heat pump will be calculated from measuring both the electrical input and the heat output.
  • Operational strategies may be adjusted based on feedback from COP calculations.

Domestic Hot Water (DHW)

  • Domestic hot water is provided by a 90 litre unvented hot water cylinder.
  • The hot water cylinder is located as near to outlets as possible to minimise tap delay.
  • The hot water cylinder is fitted with multiple temperature sensors.
  • DHW is heated by the use of a plate heat exchanger assembly (an HIU), with cold water pumped from the base of the cylinder through the plate heat exchanger where it is heated to target temperatures and fed into the top of the cylinder, heating variable quantities from the top down.
  • The plate heat exchanger if fed with hot primary water from the buffer store, heated by the heat pump.
  • The volumes of hot water heated may be adjusted based on DHW requirements (occupancy levels).
  • The rate that water is heated may be adjusted by altering the pump speed.
  • The rate of reheat will be accelerated as the hot water cylinder empties, reverting to instantaneous DHW generation when the cylinder is almost exhausted.
  • The hot water cylinder is fitted with two immersion heaters. One at the bottom to allow heating of the entire cylinder, and one located at the top allowing for rapid reheating of small quantities.
  • Use of the upper heating element in partnership with the plate heat exchanger pump allows variable quantities of water to also be heated by the upper electric element alone.

Central Heating

  • Central heating is driven by pumping heated water from the buffer store to heat emitters. when there is a demand for heat.
  • The central heating pump is switched off when there is no load requirements for either DHW or central heating.
  • The flow rate through each heat emitter (radiator or fan convector or panel) is varied in order to achieve required room temperatures.
  • Flow rates through heat emitters is controlled by a 0-10v actuator fitted on the return pipe from the emitters, located on a manifold into which all zones return independently.
  • In order to eliminate excessive start-up temperatures, heating start times will be adjusted in order to achieve target temperatures by set times. The start times will be calculated based on external air temperatures and system feed-back (optimum start).

Heat Pump Selection

Mitsubishi Electric QAVG 40kW CO2 Air Source Heat Pump

Selection

The selected heat pump is a Mitsubishi Electric QAVG 40kW CO2 Air Source Heat Pump.

Specifically designed for commercial sanitary hot water application, where gas boilers, combined heat and power systems (CHP) or electric water heating have been traditionally utilised, the QAHV provides a low carbon solution for hospitals, hotels, leisure centres and student accommodation. Utilising the natural and stable refrigerant CO2 (R744), the environmentally clean solution enables compliance to strict local planning laws and boosts BREEAM points. Compounded by the increasing decarbonisation of the electrical grid and the UK’s commitment to Net Zero 2050, the QAHV provides a high efficiency, low carbon hot water delivery solution with leaving water temperature up to 90°C.

Documentation

QAHV_6PP_AW_v2
QAHV-N560YA-HPB_Service_Manual
QAHV-N560YA-HPB_Install_Manual
QAHV-N560YA-HPB-PI-SHEET

Technical Specifications

Qavh1.png

Domestic Hot Water

Hot water to be provided using a SLIM HIU from Thermal Integration in partnership with a 90 litre unvented cylinder.

Smilextrauv.jpg
  • Fully electronic solution with anti-legionella cycle & PC connectivity for set-up and commissioning
  • Calibrated sensors for fast DHW temperature control
  • Eco / Comfort DHW modes for continuous or intelligent pre-heat
  • Compact design - 240mm (W) x 420mm (H) x 90mm (D)
  • Fully insulated compartmentalised casing
  • Stainless steel pipework
  • Open control options
  • RS485 interface
  • Optional primary pump kit Optional 24V
  • DC version
  • Optional security case with integral heat meter, landlord security valve and anti-fraud sealing kit.
  • From the same family of HIUs as the DATA - has the industries best BESA VWART figures of all time


Slimspec1.png


See http://heatweb.co.uk/w/index.php?title=The_SLIM_HIU

Central Heating

Room Controllers

Sontay Smart Room Thermostats with Temperature, CO2, Relative Humidity, PIR and ModBus

Initial requirement is for:

  • temperature, humidity and CO2 sensing.
  • hard wired
  • preferable Modbus RTU / TCP, or BACNET
  • existing units that use 0-10v and resistance can be worked with Sontay GS-CO2-S

Suggest SC-S-403000 with:

  • temperature, humidity and CO2 sensing.
  • PIR sensing
  • Modbus RTU or BACnet
  • 24v dc

Sc-x-download.pdf
Modbus Registers
SC-S Smart Sensor


Radiator Outputs

https://www.stelrad.com/radiators/standard-steel-radiators/classic-compact/

Stelrad1.png

The following outputs are based on a 33C delta T.

This comes from a 75/30C profile, with an average temperature of 52.5C, giving a 33C difference to room temperatures.

The heat pump envelope allows loads to be increased 40% over these values if ever needed.

Range Height Length Type Output dt33
mm mm Watts Btu/hr
COMPACT 300 500 K1 147 502
COMPACT 300 1000 K1 294 1,002
COMPACT 300 1500 K1 441 1,505
COMPACT 300 2000 K1 587 2,005
COMPACT 300 2500 K1 735 2,507
COMPACT 300 3000 K1 881 3,007
COMPACT 450 400 K1 174 595
COMPACT 450 500 K1 218 744
COMPACT 450 600 K1 262 894
COMPACT 450 700 K1 305 1,042
COMPACT 450 800 K1 349 1,191
COMPACT 450 900 K1 392 1,339
COMPACT 450 1000 K1 436 1,489
COMPACT 450 1100 K1 480 1,638
COMPACT 450 1200 K1 523 1,786
COMPACT 450 1400 K1 610 2,084
COMPACT 450 1600 K1 698 2,383
COMPACT 450 1800 K1 785 2,680
COMPACT 450 2000 K1 872 2,978
COMPACT 450 2200 K1 960 3,275
COMPACT 450 2400 K1 1,047 3,572
COMPACT 450 2600 K1 1,134 3,872
COMPACT 450 2800 K1 1,222 4,169
COMPACT 450 3000 K1 1,309 4,466
COMPACT 600 400 K1 226 772
COMPACT 600 500 K1 283 965
COMPACT 600 600 K1 339 1,158
COMPACT 600 700 K1 396 1,351
COMPACT 600 800 K1 452 1,544
COMPACT 600 900 K1 509 1,737
COMPACT 600 1000 K1 565 1,930
COMPACT 600 1100 K1 622 2,123
COMPACT 600 1200 K1 679 2,316
COMPACT 600 1400 K1 792 2,702
COMPACT 600 1600 K1 905 3,088
COMPACT 600 1800 K1 1,018 3,474
COMPACT 600 2000 K1 1,131 3,860
COMPACT 600 2200 K1 1,244 4,246
COMPACT 600 2400 K1 1,357 4,632
COMPACT 600 2600 K1 1,470 5,018
COMPACT 600 2800 K1 1,583 5,404
COMPACT 600 3000 K1 1,696 5,790
COMPACT 700 400 K1 258 880
COMPACT 700 500 K1 323 1,101
COMPACT 700 600 K1 387 1,319
COMPACT 700 700 K1 451 1,540
COMPACT 700 800 K1 516 1,761
COMPACT 700 900 K1 580 1,979
COMPACT 700 1000 K1 645 2,200
COMPACT 700 1100 K1 709 2,420
COMPACT 700 1200 K1 773 2,639
COMPACT 700 1400 K1 902 3,080
COMPACT 700 1600 K1 1,031 3,519
COMPACT 700 1800 K1 1,160 3,960
COMPACT 700 2000 K1 1,289 4,399
COMPACT 700 2200 K1 1,418 4,839
COMPACT 700 2400 K1 1,547 5,280
COMPACT 700 2600 K1 1,676 5,719
COMPACT 700 2800 K1 1,805 6,160
COMPACT 700 3000 K1 1,934 6,599
COMPACT 300 500 P+ 215 735
COMPACT 300 1000 P+ 430 1,467
COMPACT 300 1500 P+ 645 2,202
COMPACT 300 2000 P+ 860 2,934
COMPACT 300 2500 P+ 1,075 3,669
COMPACT 300 3000 P+ 1,290 4,401
COMPACT 450 400 P+ 243 831
COMPACT 450 500 P+ 305 1,040
COMPACT 450 600 P+ 365 1,247
COMPACT 450 700 P+ 426 1,455
COMPACT 450 800 P+ 487 1,662
COMPACT 450 900 P+ 548 1,871
COMPACT 450 1000 P+ 609 2,078
COMPACT 450 1100 P+ 670 2,286
COMPACT 450 1200 P+ 730 2,493
COMPACT 450 1400 P+ 852 2,909
COMPACT 450 1600 P+ 974 3,324
COMPACT 450 1800 P+ 1,096 3,740
COMPACT 450 2000 P+ 1,217 4,155
COMPACT 450 2200 P+ 1,339 4,571
COMPACT 450 2400 P+ 1,461 4,986
COMPACT 450 2600 P+ 1,583 5,402
COMPACT 450 2800 P+ 1,704 5,817
COMPACT 450 3000 P+ 1,826 6,233
COMPACT 600 400 P+ 310 1,059
COMPACT 600 500 P+ 388 1,325
COMPACT 600 600 P+ 466 1,589
COMPACT 600 700 P+ 544 1,855
COMPACT 600 800 P+ 621 2,119
COMPACT 600 900 P+ 699 2,385
COMPACT 600 1000 P+ 776 2,649
COMPACT 600 1100 P+ 854 2,915
COMPACT 600 1200 P+ 931 3,178
COMPACT 600 1400 P+ 1,086 3,708
COMPACT 600 1600 P+ 1,242 4,238
COMPACT 600 1800 P+ 1,397 4,768
COMPACT 600 2000 P+ 1,552 5,297
COMPACT 600 2200 P+ 1,707 5,827
COMPACT 600 2400 P+ 1,863 6,357
COMPACT 600 2600 P+ 2,018 6,887
COMPACT 600 2800 P+ 2,173 7,416
COMPACT 600 3000 P+ 2,328 7,946
COMPACT 700 400 P+ 353 1,205
COMPACT 700 500 P+ 441 1,507
COMPACT 700 600 P+ 530 1,808
COMPACT 700 700 P+ 618 2,109
COMPACT 700 800 P+ 706 2,410
COMPACT 700 900 P+ 795 2,712
COMPACT 700 1000 P+ 883 3,013
COMPACT 700 1100 P+ 971 3,314
COMPACT 700 1200 P+ 1,059 3,616
COMPACT 700 1400 P+ 1,236 4,218
COMPACT 700 1600 P+ 1,412 4,821
COMPACT 700 1800 P+ 1,589 5,423
COMPACT 700 2000 P+ 1,766 6,026
COMPACT 700 2200 P+ 1,942 6,629
COMPACT 700 2400 P+ 2,119 7,231
COMPACT 700 2600 P+ 2,295 7,834
COMPACT 700 2800 P+ 2,472 8,436
COMPACT 700 3000 P+ 2,648 9,039
COMPACT 300 500 K2 283 967
COMPACT 300 1000 K2 567 1,934
COMPACT 300 1500 K2 850 2,901
COMPACT 300 2000 K2 1,133 3,868
COMPACT 300 2500 K2 1,417 4,835
COMPACT 300 3000 K2 1,700 5,802
COMPACT 450 400 K2 316 1,079
COMPACT 450 500 K2 396 1,351
COMPACT 450 600 K2 475 1,621
COMPACT 450 700 K2 554 1,891
COMPACT 450 800 K2 633 2,160
COMPACT 450 900 K2 712 2,430
COMPACT 450 1000 K2 791 2,700
COMPACT 450 1100 K2 870 2,970
COMPACT 450 1200 K2 949 3,240
COMPACT 450 1400 K2 1,107 3,779
COMPACT 450 1600 K2 1,266 4,321
COMPACT 450 1800 K2 1,424 4,860
COMPACT 450 2000 K2 1,582 5,400
COMPACT 450 2200 K2 1,740 5,939
COMPACT 450 2400 K2 1,898 6,479
COMPACT 450 2600 K2 2,057 7,021
COMPACT 450 2800 K2 2,215 7,560
COMPACT 450 3000 K2 2,373 8,100
COMPACT 600 400 K2 400 1,365
COMPACT 600 500 K2 500 1,705
COMPACT 600 600 K2 600 2,046
COMPACT 600 700 K2 699 2,387
COMPACT 600 800 K2 800 2,729
COMPACT 600 900 K2 900 3,070
COMPACT 600 1000 K2 999 3,411
COMPACT 600 1100 K2 1,099 3,752
COMPACT 600 1200 K2 1,199 4,092
COMPACT 600 1400 K2 1,399 4,776
COMPACT 600 1600 K2 1,599 5,457
COMPACT 600 1800 K2 1,799 6,140
COMPACT 600 2000 K2 1,999 6,822
COMPACT 600 2200 K2 2,198 7,503
COMPACT 600 2400 K2 2,399 8,186
COMPACT 600 2600 K2 2,598 8,868
COMPACT 600 2800 K2 2,798 9,551
COMPACT 600 3000 K2 2,998 10,232
COMPACT 700 400 K2 452 1,544
COMPACT 700 500 K2 566 1,932
COMPACT 700 600 K2 679 2,318
COMPACT 700 700 K2 792 2,704
COMPACT 700 800 K2 905 3,090
COMPACT 700 900 K2 1,018 3,476
COMPACT 700 1000 K2 1,131 3,862
COMPACT 700 1100 K2 1,245 4,248
COMPACT 700 1200 K2 1,358 4,634
COMPACT 700 1400 K2 1,584 5,406
COMPACT 700 1600 K2 1,811 6,180
COMPACT 700 1800 K2 2,037 6,952
COMPACT 700 2000 K2 2,263 7,724
COMPACT 700 2200 K2 2,489 8,496
COMPACT 700 2400 K2 2,715 9,268
COMPACT 700 2600 K2 2,942 10,041
COMPACT 700 2800 K2 3,168 10,813
COMPACT 700 3000 K2 3,394 11,585
COMPACT K3 300 1000 K3 778 2,656
COMPACT K3 300 2000 K3 1,557 5,312
COMPACT K3 500 600 K3 712 2,429
COMPACT K3 500 700 K3 830 2,833
COMPACT K3 500 800 K3 949 3,239
COMPACT K3 500 900 K3 1,067 3,642
COMPACT K3 500 1000 K3 1,186 4,048
COMPACT K3 500 1100 K3 1,305 4,453
COMPACT K3 500 1200 K3 1,423 4,857
COMPACT K3 500 1400 K3 1,661 5,666
COMPACT K3 500 1600 K3 1,898 6,477
COMPACT K3 500 1800 K3 2,135 7,286
COMPACT K3 500 2000 K3 2,373 8,095
COMPACT K3 500 2400 K3 2,847 9,714
COMPACT K3 600 400 K3 552 1,882
COMPACT K3 600 500 K3 690 2,353
COMPACT K3 600 600 K3 827 2,821
COMPACT K3 600 700 K3 965 3,292
COMPACT K3 600 800 K3 1,103 3,762
COMPACT K3 600 900 K3 1,241 4,233
COMPACT K3 600 1000 K3 1,378 4,703
COMPACT K3 600 1100 K3 1,516 5,174
COMPACT K3 600 1200 K3 1,654 5,644
COMPACT K3 600 1400 K3 1,930 6,585
COMPACT K3 600 1600 K3 2,205 7,524
COMPACT K3 600 1800 K3 2,481 8,466
COMPACT K3 600 2000 K3 2,757 9,407
COMPACT K3 600 2400 K3 3,309 11,289
COMPACT K3 700 500 K3 782 2,670
COMPACT K3 700 600 K3 939 3,203
COMPACT K3 700 700 K3 1,095 3,737
COMPACT K3 700 800 K3 1,252 4,272
COMPACT K3 700 900 K3 1,408 4,806
COMPACT K3 700 1000 K3 1,565 5,339
COMPACT K3 700 1100 K3 1,721 5,873
COMPACT K3 700 1200 K3 1,878 6,406
COMPACT K3 700 1400 K3 2,191 7,475
COMPACT K3 700 1600 K3 2,504 8,542
COMPACT K3 700 1800 K3 2,817 9,611
COMPACT K3 700 2000 K3 3,130 10,678

Convector Outputs

These are existing units to me made use of.

Ultraslim1.png

Pump Selection

Madna3.jpg

Magna3 25-120

Magna25-120.png

https://product-selection.grundfos.com/uk/products/magna/magna3/magna3-25-120-97924248?tab=variant-curves&pumpsystemid=1603040362

Sizing

Bivalent Systems for Heat Networks

The following designs show the impact of a single 40kW heat pump on various numbers of properties. This is unrelated to the SHED, however is shown in order to give the reader a feel for the impact of even a single heat pump on real-world loads.

Each property is 2 bedroom 3 person, and 4kW heating load.

Topping up boilers are included to achieve peak loads.

Caption text
Properties % Heat Pump Design Link
20 x 2B3P 99.9% https://hw7.ddns.net/ui/hndesign?loadCID=QmNg4trTmoxkD35qj4eBWd1exKwKfbVpP3jRNgEQwZn4qB
30 x 2B3P 94.6% https://hw7.ddns.net/ui/hndesign?loadCID=QmXz5H1sdV5F1juQrQc71PLjdWCPWkHhqHkitGbC8o8B9z
40 x 2B3P 83.6% https://hw7.ddns.net/ui/hndesign?loadCID=QmPgBB6jSXehwP2ZYp7LcZNQeEyXggQM4FPgcgdQWQgZVc

Bivalent40kw

Co2graph1.png

This graph shows how the vast majority of load (for 2021) is driven by heat pumps (blue & orange), with boilers (green) used to top up.

Operational Data Policy

This section manages any policies, requirements and plans on data storage, user access, and MQTT permissions.

  • Operational data to be logged in real-time
  • Recent data points stored in controller memory
  • Options to write data logs to hard drive
  • Options to write data logs to IPFS file system (encryption policy to discuss)
  • Use of both crude and fine grained security settings by user, network, device, data type and key (MQTT ACL file functionality)
  • This Wiki project page will detail performance data for as long as SHED is in 'public' mode
  • A Private Wiki will run on the LAN with levels of user access control. This will act as:
    • the primary user interface,
    • storage space for logs locally,
    • documentation repository.
    • backups of controller software (so new controllers can be cloned)
  • VPN access to system
  • SSL https certificates on any exposed portals, and on MQTT services.
  • None of these core functions to require any licences or software costs (just add internet)
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