diesel powered irrigation II

by John A. Herbert
Hong Kong, a diesel truck coasts along the fast lane of the highway (near MegaBox) to water the plants. It was a hot day, so spraying (misting) water into the air helps it evaporate easily wasting water.

At the same time the opportunity to use rainwater from the highway directly above is loss because it is piped and needlessly dumped into the common sewer system (Hong Kong has a single sewer and storm water sewerage system), there is a better way!

Diesel Powered Irrigation

This is best practice in Hong Kong, a diesel truck hauls water for irrigation of the streetscape. In this case, filmed at Murray road by the AIA building in Central, the truck sits with its engine idling, but not all of the water actually reaches the plants, water is pouring out from the truck bed on to the road surface.

irrigation street

Another variation, the diesel truck cruises the streets at a low speed, with a helper hosing down the plants (Wang Hoi Road, Kowloon Bay, Hong Kong).

If you are really unlucky, one watering truck route meanders along blocking the only lane from Kowloon west leading into the Central/Hunghom tunnel.

 

Design vs Performance

Building regulations, Energy codes, and like tend to specify a performance parameters for the design stage, not actual building performance. The building code requires a certain OTTV  (Overall Thermal Transmittance Value) defined by w/sqm, for the building envelope. However, the delivered performance is never measured.

The energy code also requires air conditioning chillers to meet certain catalogue performance targets, however the nominal capacity is tested at steady state standard ARI conditions, unlike real life which suffers hourly variations.

zcb_45_600w

Hong Kong’s Nett Zero Energy building, known locally as the Zero Carbon Building or ZCB has a display which clearly shows (recorded 17 October 2013)  the energy consumption (277,597 kwh) exceeds the energy generated (183,470 kwh). therefore the ZCB has only provided 66% of the total energy demand, and we must assume that no energy exported to the grid.

zcb_46_600w

ABOVE: Watering the lawn at Hong Kong’s ZCB is a low technology affair (17 Oct. 2013)

Setting design performance goal is admirable, but that is only one aspect of building performance, and don’t expect design parameters alone to create high performance, low carbon buildings.

zero carbon building hong kong

ABOVE: ZCB, noon, buildings shadows the PV panels.

Actual data, for example the BEEO Cap 610 demands that every commercial building post EMSD form EE5, that provides facts, and for the first time allows comparison between performance of similar building types.

Precious water

Buildings demand a significant use of our finite resources including fuel for energy usage, water consumption, and cause atmospheric and environmental impacts from waste. Our pace of consumption cannot be maintained if some natural resources are to be spared, we need to build smarter, its crucial for our sustainability if tomorrow’s child is to be left with some usable resources.

The Green Building concept aims to reduce the environmental impact of new and existing buildings, yet environmental impact of buildings is often underestimated, a recent survey show people though buildings had little or no impact on the environment! whereas the scary fact is that 63% of Hong Kong’s Carbon footprint results from its buildings.

Some green labelling systems such as BEAM address part of the problem, but its only voluntary system. However building labelling and sustainability requires more science, including the entire life cycle impacts being assessed.

Sadly, the availability of fresh water is a critical, life threatening issue for many regions, yet developed countries, including Hong Kong frequently waste water. The photograph above shows a typical Hong Kong “Irrigation system”, a diesel fuel water tanker truck and manual hose, water efficiency is clearly not important. In this system most the water is lost in the spray, evaporation to atmosphere, or wetting the adjacent paving. Hong Kong is not alone in this regard, it occurs elsewhere, but that is not an excuse. Its a practice that needs to be stopped to avert water security and shortfall nightmares.

Water efficient alternatives exist, sub-soil irrigation avoids the short-comings delivering water into the root systems without evapouration losses, and excess.

— John Herbert, consultant, Kelcroft E&M Limited