15:00 - 15:30
Wednesday, 18 September 2019
T2.5 Optimised design for a pump-less LNG refuelling station
LNG has been used as road fuels for several years and is about to go mainstream now especially in Europe following heightened concerns about the environmental impact of traditional fuels. Among the alternative fuels, LNG is the only one really suitable for Heavy Good Vehicles, which operate on long range routes, due to its energy density, cost, and availability in large quantities.
The pace of LNG refueling infrastructure development has accelerated over the last few years but it still constitutes the major bottleneck for a full market development. In order to accelerate it, LNG station operators need new designs that can lower upfront investment as well as ongoing costs, while increasing reliability. A key source of costs and reliability issues is the liquid cryogenic pump. Pump-less LNG refueling station designs have been around for a while but have shown unsatisfactory performance concerning: (1) boil-off gas (BOG) management, (2) stock management and (3) ease of operations for both operators and users. These shortcomings are acerbated in a nascent market, in which newly opened LNG station face long ramp-up periods with low throughput. For those reasons, pump-less designs are often ignored by LNG refueling station operators, despite the cost and reliability benefits they may yield.
Over a 4-year technical development programme, we built 4 subsequent prototypes of compact, pump-less, self-service, LNG refueling stations all of which were deployed as real stations, refueling LNG refueling trucks of different brands and run by various transporters. Data from each of the prototypes were collected in real time, stored and analysed in order to produce optimized regulating algorithms and physical improvement for the next prototype. All the prototypes shared the same type of storage: a standard ISO container of 20 m3. This aspect ensured that the performance improvement could not be attributed to the storage (for instance, larger vertical tanks perform naturally better than smaller horizontal ones) but was the result of the engineering optimization of the dispensing system and the controlling algorithms.
The performance improvement from the first station (procured from an established manufacturer in the market, with no customization) to the forth (made to our specifications, fully re-engineered and optimized) included: total reduction of BOG losses (to zero, within the accuracy of the measurement systems), increase of holding time of up to 3 times, halving of minimum tank level for normal functioning, and fully automatic operations.
This paper provides the blue prints of how to optimize pump-less LNG station designs.