The article 'Wireless watch' about Sentec's Lattice solid state gas metering technology (Design Engineering, 10 March) was very interesting, but begged some questions.
Natural gas sourcing is now more variable and includes UK, two separate interconnector systems and LNG imports. Physical properties, such as Wobbe number and density will therefore vary according to limits allowed by the GS(M)R (Gas Safety Management Regulations) to reduce costly refining.
Although accuracy of the Lattice will be unaffected by gas constituents, the density and Reynolds Number may well affect accuracy.
Sentec's website demonstrates high accuracy at typical flow rates, but gas suppliers will need to know what minimum flow rate can be accurately metered. Domestic minimums can be very small indeed (pilot flames etc) down to 10 litres/hr.
Ultra-fine manufacturing tolerances on the gas passageways will be needed to maintain accuracy.
Other questions that need to be answered are: With gas and electricity together in confined spaces, is the device safe?
The growing trend is for external meters, so what is the minimum allowed temperature of this device?
Is Lattice foolproof against mechanical geeks with magnets, or the 1001 things electronic geeks can do?
Who is responsible in the unlikely event the battery fails?
Finally, the cost of Lattice per se is low, but will it be costly to wirelessly transmit indication of gas flows both in-house and remotely?
The greatest obstacle to real-time meters helping fuel saving, though, is the relationship between gas rate and and money rate — and the latter will not, and cannot, be directly indicated.
Not only do prices vary between suppliers but they are constantly changing. The greatest cause of carbon profligacy is the crazy way all utilities' energy is priced — the first quantity of gas (or electricity, oil or water) used in a period is charged at a high rate, followed by a much lower price for further usage. At this time, the government must be mad to preside over utility pricing where the more we use, the cheaper the energy.
Anybody trying to save energy by installing green technology only saves on the lowest-priced fuel, which is not much of an incentive.
And energy is subject to five per cent VAT which is a reversal of all the principles of our tax and vehicle excise duty. It would make sense to reverse the way energy is priced and to blend in the fixed metering costs.
PH Field
St Albans, Herts
Points to watch
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