Air Conditioning Leakage

by John A. Herbert
condensate

Spring has arrived, the humidity is increasing and air conditioning and their power consumption start in earnest.

Air conditioning systems rely upon converting electrical energy at the central chiller to chilled water, yet these veins, the chilled pipes are often hidden from view, deep inside the building behind locked plant room doors. The chilled water piping should deliver cold water from the chiller at approximately 7 deg. C to the AHU’s.

However, the photo above is a big problem, the chilled water piping is insulated, covered with vapour barrier, and finished with aluminium cladding. However, condensation is clearly visual and that equates to lost energy. If it not repaired the water wicks along the piping and thermal insulation, causing more condensation, increasingly wasting more energy.

To rectify the wet and damaged thermal insulation needs to be cut back and removed, piping cleaned and insulation replaced, and wrapped with a new vapour barrier, and re-clad. the new vapour barrier is key!! to prevent moist air contacting any surface, including the insulation, having a lower dew point temperature.

Energy Efficiency is Not Rocket Science

Hong Kong is a great location, indeed I am fortunate to meet a great number of smart, intelligent people that travel through Hong Kong, this week alone I met a Government Minister, a project developer, and financiers from the energy sector.

Its dark down here

I am equally sure that for all the talk about energy efficiency improvement projects, not many people have actually spent as much time in plant rooms as I. Continue reading

Saving Energy in Steam Systems

Opportunities to lower operating costs for Steam systems using energy efficiency improvements – there are plenty opportunities to improve industrial energy efficiency for steam systems in China, and elsewhere in Asia. And some projects may also qualify to earn extra income from a carbon credit (officially known as CER – Certified Emission Reduction) under the Clean Development Mechanism (CDM).

I see the potential for the wider application  of CDM AM0017, which is the official CDM methodology for calculating the Steam system efficiency improvements by replacing steam traps and returning condensate.

System Systems
Steam is still a marvellous high density medium for transporting heat energy, and an essential part of industrial process needs, however a high pressure fluid, at temperatures up to 500 Deg C needs to be respected.  Twenty years ago I cut my teeth on steam projects in the United Kingdom, a typical hospital project demonstrates the utility of steam, where it is used for autoclaves, sterilising, catering, cleaning, domestic hot water, humidification, and also heating systems.

A steam system, consists of four main elements:

  1. Steam Generation
  2. Steam Distribution
  3. Steam Traps
  4. Condensate Return

energy efficient steam and condensate systems

Energy Audit Opportunities
An energy audit should examine the whole steam system, from generation through to point of use to identify wasted energy, and identify any cost effective improvements. You’ll notice immediately that unlike other piped systems, the steam flow and condensate return have to be handled separately.

Steam Generation
Steam generation means creating steam using fuel typically coal, oil, or gas, although electricity is sometimes used also.  Water is heated from atmospheric pressure to the designed steam pressure for use in the facility.  Operating boilers at maximum efficiently, including monitoring air flow, improved firing controls optimise the use of fuel and can yield good results. Power stations often use coal fired boilers, and naturally have a low thermal efficiency thirty percent is common, so there are opportunities to utilise that wasted heat energy for an local industrial process.  Opportunities for energy savings would include recovering any waste heat energy for example from flue gases, or blowdown to pre-heat the any fresh (raw) water. For large industrial plants it could be possible to use higher pressure steam to drive electricity generating turbine, and use that lower pressure exhaust for process purposes.

Steam Distribution
Steam distribution is the transfer of your steam now under high pressure from the boiler to the point of use with minimising losses, Steam is not mechanically pumped, its movement driven from the inherent pressure difference, high to low pressure.

It is important that the steam distribution system does not reduce or lower the quality (dryness) of the steam because that lowers the heat energy. Unlike other piped systems the steam can travel at high velocity, upto 30m/sec, and the self drainage of the steam pipework is critical to effectively deliver dry steam, and is air vented for start up conditions.

Piping configurations that dip under obstacles such as other services and beams would create a natural low point where condensate will accumulate impacting the steam quality, and provide a source for damage by water hammer. Particular care is required for the configuration of expansion joints to ensure they are self draining.

Opportunities for energy efficiency improvements in the steam distribution system include minimising heat losses, reducing piping routes, where possible design out low points, and economic insulation.

Steam Trapping

Although Steam trapping could be considered as part of Steam Distribution, or Condensate Return, the problems are so common and distinct Steam trapping deserves a separate section.

The steam trap is the gateway between the process outlet and the condensate piping system, very often the traps leak due to internal blockage.  Most steam traps have a small orifice that can easily become blocked by debris and fail in the open position. A failed steam trap wastes energy due to causes increased heat-up time, and lengthened the product cycle times because the potential latent energy in steam passes straight though the process and is lost in to the condensate system.

Condensate

Bad design or maintenance panic (just to get production running again) causes another common problem, the wrong type of steam trap, and facility operators are unaware that the wrong type of trap is wasting energy. In some circumstance, poor management can cause injury to operators.

Traditionally,  condensate steams were fitted with a special type of fitting known as a sight glass so operators had the opportunity to visually check that water, and not steam, was flowing in to the condensate line.

However, the sight glass had many disadvantages.  Over time the “glass” viewing port become obscured and unusable. Also some sight glasses were installed in such a location that the operators couldn’t physically access the sight glass to check it.  To overcome these shortfalls a different type of steam trap monitor was invented to provide remote monitoring of condensate or steam flow, for example, the Spira-Tech manufactured by Spriax Sarco, other companies provide similar systems.  This type of trap monitoring system immediately alerts the facility operator that they have a faulty trap, and importantly its exact location.

Condensate Return
After the steam has been used in the facility process to heat a product, what remains is the Condensate (hot water). It must be noted that still many industrial steam plants don’t have any condensate return system! Why is that a problem? because it millions of litres of hot water are wasted, in additional “cold” raw water needs to be purchased to replace it.

Where uncontaminated condensate can be captured, it can be sent through insulated piping back to to the boiler for reuse. In my experience, next comes the most commonly asked question “What percentage of condensate should be returned to the steam boiler plant?” In a perfect world 100%, yes, all the condensate should be returned to the boiler, since the condensate contains up to 20-30% of the heat energy used to create the steam, returning it to the boiler saves both fuel and raw water.

However, there are no targets written in stone, 100% is an ideal goal but it is simply not practical in the field, any system that returns less than 70%-80% condensate warrants investigation.  It is worth noting that condensate flow varies, during start-up approximately twice the flow rate of normal operating conditions is experienced so condensate handling must account for higher loads at start-up. Opportunities for energy efficiency improvements include increasing the quantity of condensate returned to the boiler, eliminating leakage, and economic thermal insulation for the condensate piping.

Carbon Credits
Energy efficiency improvements are driven by the economic imperative, lower facility operating costs. In addition to the lower costs, saving fuel also reduces the demand for finite fuel resources such as oil and gas.  Another potential income stream from energy efficiency improvement projects in developing countries is provided by the Clean Development Mechanism (CDM).  AM0017 is the CDM methodology for calculating the Steam System efficiency improvements from replacing steam traps and returning condensate. That means the saved energy can be translated into a carbon credit which has a real monetary value, and can be sold on the carbon market.

by John A. Herbert, Consultant

Energy Audit – more wasted light energy

1.00 pm, Sunday, 18 January 2008, Kowloon Bay, Hong Kong

It is a beautiful bright sunny Sunday afternoon, the store is obviously closed, and the shutters are down. Yet all seven (7) exterior lamps are burning brightly, here is a photograph captured with my camera phone.

Did the owner forget? or believe it would not make a big difference? Did someone consider the extra coal that would be burnt at the power station and its resultant pollution to keep those lights on?

This raises the thorny issue, the true cost of power, can we continue to overlook the generation externalities? The social cost of pollution created by power generation in Hong Kong is presently estimated to be in the order of HK$ 6 billon (US$ 740 million) per year, but that cost is not priced into the consumers energy charge, its paid by the tax payers. The Hong Kong Government verbally advocates a polluters pay policy, however the reality is very different, often relying on the tax payer to foot the bill.

Energy Audit – more about lighting

Continuing the lighting audit theme for another post – A simple but often overlooked option for controlling energy costs is thoughtful design of the lighting circuitry and control system for lighting, particularly exterior lighting.

Exterior lighting control is hardly rocket science, low cost circuitry with a contactor and photocell is a preventative measure,  keeping the the external lighting from operating during bright day time hours saving countless kilowatts, and the maintenance cost for re-lamping.

Unfortunately, as the exterior area of the car park as the photograph indicates, poor design coupled with lowest first cost mentality means building owners often end up with only one control circuit operating both indoor and outdoor fittings simultaneously. Of course, this causes waste due to the unnecessary operation of lights during the day light hours.

It is easy to zone other areas too, in the car park example, covered parking having a perimeter with abundant natural light don’t need electric lamps burning during daytime hours.

If you opt for photocell control,  do ensure the photocell location is accessible for easy cleaning.

Energy Audit – its not just about the lux

It is not just about the recording lighting level (known as LUX)

lighting energy audit

Lighting efficacy – Energy audits for buildings, typically include a lighting audit. But just recording the lighting level (known as the lux level) in the various rooms is not enough. We need to assess the effectiveness of the installation.

During a recent energy audit several lighting fittings (as shown in the photograph) were discovered. Perhaps discovered is the wrong word, the high intensity fittings were plainly obvious.

Pairs of uplighting fittings were installed close to each other, and very close to the ceiling.

These fittings didn’t add any value to the illumination of the space, as you can clearly see these intended uplighters only created an intense, localised pool of light (and heat).

Based on operating 3,600 hours per year, each fitting wastes HK$ 660 per year in electricity. Just measuring the lighting level is not sufficient for an energy audit, in this case immediate removal was recommended saving electricity.

Also remember that in air conditioned rooms removing lighting fittings not only lowers the electricity consumption for lighting, it also lowers the heat gain which in turn reduces the load on the air conditioning system. As a rule of thumb, eliminting 1 Kw of lighting lowers the total electricity consumption by 1.3 kw.

Green Bank – implementing energy audit findings

New Resource bank (in USA) is the country’s first “green” bank and they love helping in green people in green ways……. read the full article here

It is a positive step that at least one bank in the US is finally being to understand. However if you don’t have access to a green bank where do you turn? First ask your local energy consultant, they have the knowledge and contacts to point you in the right direction.

For economically viable large projects, let’s say US$ 10 million and up sourcing finance is not the major challenge, there are several options in the market. However, the important smaller schemes often struggle, and find difficulty to securing funding, in reality nobody is really interested due the transaction cost.

I have spent time explaining the an energy efficiency finance model to banks who seem to uninterested, prefering to opt or lets say demand upfront collateral, ignoring the efficicency savings as a future income stream. Luckily, we have an Mr Xu, an energy specialist at ADB Hong Kong, who we hope will help the re-education process.

Energy audit findings

Energy audit findings – the photograph above is a section of a damaged coil from an air conditioning unit. It is obviously a badly damaged, the aluminium fins have been stripped away, revealing the structure of the refrigeration tubing beneath, absolutely necessary for coolant-to-air heat exchange. However, since the air conditioning is still “technically working” it seems no repair is deemed necessary to restore the lost heat exchange area, and lost efficiency.

Specification Note: Actually this is a common problem, and easy to avoid – insist upon a heavy gauge, say 25mm x 25mm GI mesh over the exposed coil area to provide mechanical protection. With a large open grid, the mesh would not impede the air flow. It will protect the delicate fins from unintended damage.

Don’t forget to check your utility tariff

DON’T forget the electricity tariff – It is easy to overlook the painless cost savings achievable by simply choosing the correct Utility Tariff for your facility or building.  A tariff is the published rate for electricity charging, typically utilities offer different charging schemas for low, medium and high consumers.

Tariff Analysis is a scientific based approach, examining your the utility bills to identify the optimum tariff for you, that the tariff with the lowest cost.

Where the utility company permits summation metering, and the facility has more than one power meter, re-analyse using the totalled data – using all the meter readings, to check and identify if summation metering provides a beneficial tariff.

Remember that tariffs change frequently and without notice,  so its wise to ensure that you order a Tariff Analysis at least once per year.

Whole System Thinking

Changing the world is difficult, to change custom and practice is one tiny step on the journey.  One of the primary reasons for poor building performance happens early in the design process and often before the engineers are consulted.

The Old Way
At the earliest stages of the process, at the critical juncture whilst conceptual ideas are still being formulated, a proposed scheme is presented sold to the owner or developer, before the engineers have any say. Unfortunately, once that scheme has received the official blessing, the fate of the of the buildings operating costs is virtually sealed.

Change is good but not in building development,  the designer and team had already lived with the plan for a few weeks, they are invested in it success.  Any subsequent “change” that could potentially undo that work, and perhaps might require the designer to modify the the layout or the facade is typically rejected. The designer moves on, there is a firm scheme, then other consultants are summoned to join his project team. It does not happen in every case, but that is a fairly typical MO.

Another Way
There is another way, a more productive way WST (Whole System Thinking) is an integrated approach to engineering design that challenges past assumptions made everyday. If evidence is needed here is a link to a cost Summary Sheet (1 page PDF format) incidentally is protected document, the password is kelcroft.

Evidence
Using the WST principal this heat rejection solution provides the same capacity with less CAPex investment, and provides a lower OPex for the lifetime of the equipment. Yes, it did require more engineering effort than the typical methodology, because the system needed to be properly designed. The WST approach exceeds incremental 2-3% savings, delivering more than 30% reduction in first cost compared to the typical design.

If concepts designs are locked down early, the opportunity for WST is lost along with the chance of lower operating costs and reduced carbon consumption.

Putting this in to a future context, it has been estimated that urbanisaton will continue to expand in China increasing the number of city dwellers upto 0.9 billion in 2025, building sustainably is the only solution.

John Herbert, Consultant, Kelcroft