December 1996
Second AJAX for Southern Water
New Biogas Compressor Packages run quiet and cool.
120kWe Twin AJAX available from 1997
All engines running well on High H2S Biogas
Solar Powered Office aims for Zero CO2 Production
[Practically Green News Index]
The second AJAX powered CHP unit for Southern Water leaves for Ham Hill Treatment Works. Rated at 115kWe on variable calorific value fuel with H2S levels at 10,000ppm. The engine produces electricity, hot water for digester heating and a 5000:1 reduction in odour from the biogas.
Ham Hill CHP unit, commissioned and running.
The Ham Hill engine installation was the result of Southern Water intensively testing an AJAX engine on high H2S biogas at Canterbury. The Ham Hill unit provides hot water for heating, 115kW of electrical power net of parasitic loads and boasts a number of component reductions compared to the Canterbury unit. The fuel gas pressure regulator and variable orifice throttle, (a site of potential problems during digester foaming incidents) have been replaced by a Digital Throttle (TM) which leaves the pipe work from the engine head to the gas compressors free of any active components during operation. The safety shutdown (main engine fuel shut off valve) is retained and the system modulates fuel flow to compensate for variable calorific value fuel.
Adjusting the overspeed trip on the Ham Hill engine.
Power transmission is achieved by the most efficient toothed belt drive system on the market. This produces a very smooth connection between the engine and the generator, removes a gearbox, two couplings, a powder clutch and plate clutch from the drive chain - the result is a simpler system with lower power losses through the transmission.
Hot water circuits have been refined and tuned to the need for digester heating at 75 degrees C. with low losses.
Airflow to the engine has been increased to give 10% more power output from the gas injected 2 stroke engine at 392rpm - slightly faster than the Canterbury unit. But perhaps the most significant development is the air suspension system which has provided better than 99.9% vibration isolation between engine and ground - necessary as the whole system is located in a 1960's brick building on bogland with very few piles!
Gas compressor package at Ham Hill
We are supplying really robust and whisper quiet compressor packages for biogas applications. These are supplied in first duty/ second duty skid mounted packages to our own exacting specification based on 12 years of operating experience in this harsh environment. The equipment boasts excellent H2S corrosion resistant temperature and pressure sensors for continuous status reporting. These units are de-rated to operate cool with permanent pressurised oil lubrication, extremely efficient bearing seals and generously sized motors. VERY reliable, these units are a joy to operate.
A new engine has been added to the range and we expect this to become the standard choice at the lower end of power requirements in the future - a smooooth 2 cylinder 120kWe engine. These and other larger units are available with acoustic boxes from 1997 onwards giving all the robustness we have come to expect of an AJAX unit with a quiet smooth operation suitable for today's stringent environmental requirements.
Canterbury AJAX gas engine.
The engine above, built for Southern Water, Sturry Road STW, Canterbury is running 162-166 hours per week if gas is available from the digesters - four years after installation. After generating over 4.5 million kWh of electricity, and about twice as much hot water for digester heating this unit has proved to be more reliable than the digester equipment that delivers the fuel. It has a long life ahead of it - possibly 40 years or more. Annual maintenance costs are less than 2,000 UK pounds . ($1.5=1UK pound). Service requirements consist of a daily visual check (if possible), weekly oil tank reservoir fill and greasing plus a spark plug inspection (2 champion w18 plugs at c.$4 ). The annual service takes 10 hours work for a pair of engineers. A five year service can add another day's work. Every ten years or 100,000 hours the cylinder is changed and every 20 years or 200,000 hours the bearings are relined.
Solar House -the new headquarters of Practically Green Environmental Services
Possibly the most advanced thermal structure in the UK! The design heating requirement in the sub arctic tundra environment of Northern Ireland is 0.5kW per 1000 square feet (annual average.) However, the system goal is to produce no net carbon di-oxide across the boundary of the site. This project is supported by the European Regional Development Fund.
The Solar House sewage works - no motors! Psychrophilic digester + root zone treatment plant followed by fish pond prior to discharge to the local stream at 20/30 std.
Practically Green News is the newsletter of Practically Green Environmental Services. Practically Green, Practially Green News and Practically Green Environmental Services are trade marks belonging to Dr.L.K.Gornall. AJAX is the trade mark of Cooper Energy Services. The articles in this newsletter represent the views of Practically Green Environmental Services. Whilst every attempt is made to represent products and services accurately, errors can occur and no liability can be accepted for errors and omissions. This newsletter is not a contract.