Super efficient, low carbon footprint, etc etc - ideas?

[Makeit go Right]

A customer is interested in a super-dooper efficient, low carbon footprint, no-threat to the planet, aircon system for their office building (about 50kW load) and asked about CO2 refrigerant systems - Anyone know of any such packaged units available in the UK?

As far as I can establish, there are some cascade-type systems becoming more popular, involving CO2 on the evaporator side and either Propane or Ammonia on the Condenser side, but I guess these would be more appropriate for industrial or large waterchiller systems. And the heatpump aspect looks complicated/unworkable.

What's the word on these types of systems for office buildings, please? Does anyone have any experience or info on this?

Any other super-dooper efficient type of system that could be considered? (I assume the building is composed of general offices with a computer room - nothing unusual.)

I must say, off the cuff, I would be looking at Mitsubishi and Daikin systems for high efficiency regular VRF systems.

[Brian_UK]

Any thoughts on using gas fired absorption water chillers to provide the end product?

[hendrag]

CO2 is not used in aircon as a primary refrigerant by anyone YET but in refrigeration its tarted to be used, i believe there are 2 supermarkets running on it. CO2 will only take over once the 400 refrigerants are banned which hopefully isnt for a few years. The hydrocarbons cant realistically be used due to regulations on concentration due to flamaabliltity. The best bet is to use chillers running off co2 or ammonia as suggested or sod it and go VRF these things are really efficent theses days.

Good luck and if you need any more alt refrigerant info contact me. All the manufacturers are really working hard on these issues but its costly so watch this space in the future.

regards

Hendrag

[Makeit go Right]

Thank you Brian and Hendrag for your comments. Yes, the CO2 seems to be useful for larger systems, combined with another gas (Ammonia/Propane etc) on the condenser side, or maybe used in conjunction with water FCUs. These being more complicated (more expensive) systems and operating at higher system pressures (stainless steel pipework etc) it looks to confined to the larger system league for the time being, at least.

If the green wave continues to drive the industry, it would seem that the Care refrigerants/ HCs, which have zero ozone depleting potential and zero global warming potential, will soon be in vogue. AIUI, use of propane (R290) is limited to 2.5kg per sealed system in commercial applications (ACRIB 2001) so that particular gas has some limitations.

It sounds like my customer will need to consider options involving several Care-gas systems, compared with the most efficient VRF systems available.

Anyone like to suggest which would be the most efficient VRF system for an application of say, open plan offices at 40kW and a Computer Room of 10kW (sep system)?

Thanks for any further ideas/helpful comments.

[eggs]

Toshiba now recommend that you put your server room on your VRF/V. Apperantly it helps with the efficiency due to the constant cooling demand within the system. As far as reliability, with a 50kw load you are going to have at least 4 compressers and a few outdoor boards to go at before the server room cooling fails.... It's a no brainer if you think about it.

Stick in a Tosh

Eggs

[The captain]

Another common system is evaporative coolers .

[Thermatech]

I tend to find that most office applications require mainly cooling even during cold winter weather. Typically the office space just needs some pre heating in early morning but as soon as staff arrive then lights & computers are turned on. The heat load by mid morning is such that cooling is required for the rest of the day.
Most of the VRF manufacturers do heat / energy recovery ventilation units which are small enough to retro fit into existing ceiling space & therefore do not need large air handling unit or large duct installation.
The premium brands also can electronically intergrate the HRV units to work with the VRF system control system.
The HRV units can automatically provide full fresh air to the occupied space when the outside air is colder than the room set temperature therfore providing free cooling. With uk day time ambients being below 21 deg C for more than 50% of the year this can provide great energy saving.When the VRF system does need to be providing heat to the occupied space then the HRV changes to heat recovery mode & pre heats incoming air by recovering the heat from the exaust air.
As the current Part F ventilation regulations require 10 l/s per person for office applications you would need lots of fresh air anyway to comply.
So using HRV means you get 1/ free cooling 2/ ventilation heat recovery 3/ better indoor air quality 4/ comply with current ventrilation regs.

Mitsubishi Electric also do a heat pump boiler to provide domesic hot water. It can be fitted to the the heat recovery VRF system like any other indoor unit & then all the time the system is cooling which it will be most of the time in most office applications it will be providing free hot water for the toilets & kitchin without the need for solar panels.

All of this is tried & proven technology which alot of contractors have been installing, commissioning & servicing for 15 years or more in the uk so no worries about being used as a test site for some unproven technology.

[Thermatech]

Toshiba now recommend that you put your server room on your VRF/V. Apperantly it helps with the efficiency due to the constant cooling demand within the system.

Eggs

Be very careful because there are a number of problems with using this type of heat recovery even though on first inspection it looks like a great idea.

1/ VRF indoor units are designed for comfort cooling & tend to have sensible heat ratio of about 0.75 & therefore have small coil size & low air volume. They realy need some latent heat to work properly.
But computer room has 100% sensible load & an indoor unit designed for this application would have much larger coil size & much larger air volume.
2/ Unless you install humidifiers ( not so good for energy efficency) the indoor units stop every few minuits on coil frost prevention because the computer room humidity get very very low usually around 25 to 30 % RH. You really need 45 to 50 % humidity to ensure the units do not cycle on coil frost prevention mode.
This is ok all the time the VRF outdoor unit is running the compressor to provide refrigerant to other indoor units in the occupied office because the compressor just ramps up & down to match the load. But during the night time the computer room unit will be the only unit running & then every few minuits the VRF outdoor unit compressor will start/stop/start/stop.
The compressor & inverter will use up a life times start / stop cycles in a very short time & then the customer is into funding a replacement compressor/inverter.
3/ You would be operating a VRF 50KW outdoor unit at part load 24/7 so the VRF outdoor unit will run up its expected life time run hrs in about half the time it would otherwise if it was runnuing 7am to 7pm & 6 days per week.
This size outdoor unit will be about 6K cost.
4/ The actual benifit of the heat recovered is limited to when the office is in need of heating so that the heat can be recovered from the computer room & used for heating the office. But as already stated most office applications only need one or two hours of heating for early morning warm up & only during cold winter months.
So you are running a 50kw outdoor unit 24/7 just so you can recover 10kw of heat from the computer room for two hours a day during winter months.
The heat recovery cost saving is possibly not enough to pay for the premature failure of the compressor.

However if you can interlock the VRF indoor unit in the computer room so that it only works when the office is calling for heating then you will get that heat recovery saving & prevent the excessive run hours & excessive stop / start cycle on the VRF compressor.
You then need to also fit a 10KW split system to operate the rest of the time. ( replacement split system much cheaper than the outdoor VRF unit )
This has the benifit for the customer because he will have 100 % back up for the computor room if the VRF or the split system stops on a fault.

Sales people & consultants like to suggest cooling computer rooms with VRF but in there ignorance they simply do not understand the long term consiquences & will be nowhere to be found when the system fails. But the service engineer will have to face the enduser with the unpleasant reality of unexpected maintenance cost.

[techguy]

Hi ,

Sanyo and Diakin do CO2 water heat pumps but these are used for heating /chilling water and would involve installing fancoils etc I'm not sure they would be suitable the Sanyo system is primarly a heat pump to supply hotwater/underfloor heating systems. (not sure about Diakin)

Mitsu have a ground source Vrf system but the cost of the bore holes or trench to bury the ground source accumlator could be very high. There was an artical in the RAC magazine recently detailling this.


Sanyo have a GHP VRF system operating on Natural gas or Propane. Comes in 3 pipe 56KW outdoor and any configuration of indoors you may require.
2 pipe 6No model sizes from 22kw to 71 kw. Above 28 Kw there is an option to reclaim up to 19 kws of free hotwater for domestic purposes at real temperatures up to 75 degrees celsius. Even when the outdoor is in the heating mode and the ambient is above 10 degrees celsius.

This system also has the added advantage that it never needs a defrost cycle and will give full rated output in ambients down as low as -20 celsius.

In Ireland the usual saving on Carbon emmisions is between 20 and 30 % against electric VRF and Chillers but not sure about the UK you guys have some nuclear power so I would imagine this figure is somewhat lower.
Try www.sanyoaircon.eu and downlaod a brochure you can get the mitsu info from their site www.mitsubishielectric.co.uk


Failing the above theres always natural ventillation open a window heheheehe