Pollution is also a major problem – both the larger lakes and lakes in cities are polluted, some of them seriously, and water quality is continuously decreasing in both urban and rural areas. At present, 50% of the surface water in China does not achieve acceptable standards. Furthermore, most lakes in cities are unfit for consumption because of the domestic sewage and the wastewater from factories that is discharged into them.
The quality of underground water is also a matter of concern. According to a survey conducted in 118 cities by the Ministry of Construction, 97.5% experience pollution at some level, and 40% are seriously polluted.
The conflict between the limited resources and the increasing demand for water is made worse by rapid urbanisation. Using effective measurement techniques and improving awareness of the need to conserve water has therefore become one of the important tasks for the water supply industry in China’s cities.
Improving measurement management for domestic water consumption is an effective technique used to reduce waste and unreasonable consumption, and consequently to rationalise water consumption. This measurement management has two aspects: one is to record the water consumption of every household manually, and then gradually implement a stepped tariff for water, so as to improve awareness of the need to conserve this resource. The other is to extend the use of highly accurate water meters, to reduce waste as a result of dripping taps, for example. This will allow utilities to reasonably forecast the quantity of water supply, to control domestic water production, and to reduce the difference between production and sales.
In recent years, the goals set out by the Ministry of Construction – to record water consumption for each household manually by installing one meter per household, and to charge for metered consumption – have substantially been met. However, problems such as the considerably increased workload for utility staff, and the reluctance of residents to allow meter readers into their homes because of the disturbance to their lives and the concern for their security, have become increasingly common.
Recently, in order to solve these problems, the Ministry of Construction proposed two schemes – the installation of prepayment water meters, which allow users to pay in advance, and remote meter reading, which allows meters to be read without gaining access to residents’ premises. China is a very large country, and thus there are various different rules and regulations in different areas regarding the approach to be implemented when measuring and charging for water consumption. In this article we will focus on the issue of water meters for domestic supply, and discuss the application and development trends for automatic meter reading technology.
THE CURRENT SITUATION
At present, most meters used by domestic water supply corporations are multi-jet, horizontal screw damp/dry class-B mechanical meters, which are read manually. Since the implementation of ‘one meter for one household’, the workload has increased 5 to 8 times.
Furthermore, the class-B meters cannot measure consumption in situations such as dripping taps, because of their low accuracy levels, and water wastage caused in this manner is therefore easily overlooked. This results in financial losses for water companies; there is a significant difference between domestic water production and sales.
In order to be able to read meters without gaining access to residents’ premises, several remote meter reading techniques have been used in recent years, including both wired and wireless intelligent automatic meter reading techniques.
The rapid development of technology has seen new types of intelligent water meter (both remote and prepayment) being installed as a substitute for manual meter reads. Deployment of these intelligent meters can be expanded according to local circumstances, with the aim of reading all meters remotely, thus solving the problem of disturbing residents.
In addition new technologies are being introduced to make it easier for households to pay for service consumed. Water companies today offer multi-channel payment services such as direct account transfer, online payment, and payment by telephone. This has been accomplished by expanding and improving the management and service functions of their computer processing systems, including establishing corporation intranet and public information platforms, and by co-operating with banks to develop networks that interface with the utility. The aim is to establish a new model of domestic water marketing and management; to achieve the goal of e-commerce services; to enhance customer service; and to fully use public service systems.
Today meters can be read from outside the customer’s premises, while the customer is able to pay for these services from his own home.
PROBLEMS WITH ACCURACY
We have already noted that the class-B water meters used in recent years are low in accuracy. As a result, when the quantity of water flow is lower than the ‘start level’ of the meters, the meters do not measure this flow. In the industry this is known as ‘reasonable water theft’. A recent survey has shown that the figures recorded by sub-meters in each household are 16-18% lower than that for meters in each building – the waste of water is substantial.
Therefore, increasing the use of high accuracy water meters is both a way to solve the problems resulting from low precision and a means of reducing the difference between production and sales. Using high precision class-C water meters will mean that the difference between production and sales can be reduced by 3-5%. These single-jet class-C mechanical meters can be used in a wide range of circumstances, and the trend in China is to combine this type of water meter with the use of remote meter reading.
INTELLIGENT REMOTE METER READING
Water utilities have adopted two approaches to marketing this resource – ‘consuming first, charging second’ and ‘charging first, consuming second’. There are two types of meter system available to consumers – the remote metering system and the prepayment system. Both are intelligent meters, and both have remote meter reading functions.
The technology of choice for companies active in the domestic water supply industry in China is the traditional credit system using remote meter reading equipment. It is seen as being more socially acceptable, and thus more appropriate for application in cities.
Intelligent remotely read meters perform two functions – they collect and send data. One type of mechanical water meters collectively records data through impulse measuring, memory, processing and data transmission. The other type works by directly reading, memorising, and sending the figures from the base meter.
Intelligent remote meter reading systems can be divided into the following types, based on different approaches of operation and communication:
- Communication using SMS or text messages
- Digital electronic meters
- Meters using smart cards, either for prepayment or for remote meter reading
- Communication using PLC (powerline carrier) technology
- Wireless meters that communicate using RF or GPRS
- Direct reading meters that use, for example, a digital video camera to read the data.
A further enhancement to the meter reading system is to send meter readings directly to the utility from local data collectors, using various technologies such as telephone, wireless networks and GPRS. This enables fully automatic meter reading to take place.
The main techniques for remote data collection are impulse measuring and direct reading. At present the impulse measuring approach is more widely adopted, and the main devices used are reed pipes, Hall component and Wigan. Direct reading, however, has several advantages over impulse measuring and is likely to be more widely used in future.
Wired intelligent remote meter reading is a mature technology that offers high reliability. There are also disadvantages, however, including the fact that it is relatively difficult to maintain, especially when cables have to be laid to connect meters in old buildings or in residences that have completed their interior decorating.
Meter reading using PLC offers several benefits. The existing electricity cables can be used, so it is easy to install and does not need maintenance. It is particularly appropriate for meter changing in old buildings and refurbished residences. The problem of interference from electric devices in households can be reduced to below 10-5 by adopting interference prevention techniques. This is a communication channel that has promising market potential.
Wireless communication systems are also easy to install without the need for cables, but the 433MHz frequency used at present does not allow the capacity to exceed 10mW. Moreover, data transmission is vulnerable to disturbance, especially in high-rise buildings built of reinforced concrete, where communication stability and reliability are low because of the existence of blocks and blind zones. In addition the problem of electromagnetic pollution needs further discussion, and battery lifespan is another issue that affects the use of the system.
China’s goals for the future are to establish a meter reading network using intelligent remotely read meters and outdoor data concentrators, supplemented by prepayment meters. In addition some cities will plan to introduce automatic or semi-automatic meter reading systems using portable meter recording devices.