Airships

businessGreen.com has reported that the government’s former chief scientific adviser, Professor Sir David King, told the World Forum on Enterprise and the Environment conference in Oxford that helium balloons (airships) would replace aircraft as a key part of the global trade network as a way of cutting global warming emissions.

The article mentions some of the other benefits of airships such as not needing to use airports if fitted with “lifts” to pick up and land cargo – in turn, this would reduce the need for trucking goods to and from transport hubs.

It may come as a surprise that the Zero Carbon Britain 2030 – A New Energy Strategy report published by the Centre for Alternative Technology contains a section about airships.

SkyCat's SkyFreight Airship

SkyCat's SkyFreight Airship

For ease, I have copied the report’s airship section below (for those of you who wish to read the section as part of the report, it begins on page 128 – shown as page 144 in Adobe Reader).

“Airships
While not part of the core zerocarbonbritain2030 scenario, airships are an interesting potential way of meeting transport demands, specifically semi-perishable freight. Airships use hydrogen or helium, both elements lighter than air, to provide lift. They have much lower greenhouse gas emissions than aircraft because they do not need to use energy to generate lift; they go slower; and fly lower.

“Most of the modern airship designs are actually hybrids, which incorporate lighter-than-air technology with aerodynamic lift. One example is CargoLifter’s proposed CL160 airship. It is estimated that this airship’s greenhouse gas emissions are 80% lower than that of a Boeing 747 (Upham et al., 2003). A similar figure is given by Hybrid Air Vehicles (HAV) for their SkyCat range of airships. HAV report that their SkyCat design consumes an average of 70% less fuel per tonne-kilometre than aircraft (HAV, 2008).

“Furthermore, airships could conceivably be powered by hydrogen fuel cells or liquid hydrogen. When using hydrogen from electrolysis with electricity from renewable sources this would reduce emissions to almost zero. Because airships fly at a lower altitude than jets, the water vapour they give off does not have the warming effect that it does when it is released from jets, so flying them on “green hydrogen” has real benefits for the climate.

“Airships are unlikely to be able to replace high-speed passenger jets on long-haul flights because they are too slow. A Boeing 747 has a cruising speed of 910 kilometres per hour (kph) and most projected airships have a cruising speed of between 100 and 150kph. An airship flying from Britain to the USA would take several days to get there. The facilities which would be required (beds, space to exercise etc) would make passenger numbers on each airship low and therefore would make it an expensive form of transport. It is more feasible to imagine that scheduled short-haul passenger services might be a possibility, but airships will find it difficult to compete with high-speed trains, which are two or three times as fast and also likely to be cheaper.

“However, airships may be a really viable option for freight transport. Airships can compete in the air-freight sector on speed because air-freight is not as fast as is often assumed. The mean delivery time of airfreighted goods is 6.3 days because of the need for goods to be transported to and from the airport (Upham et al., 2003). The logistics are exacerbated by the relative scarcity of suitable airports for cargo jets – in the UK there are only about five civil airports which can accept a fully-laden Boeing 747 (ibid.). Airships can carry goods “door to door” because they require very little infrastructure to dock and discharge their cargoes (ibid.). The CL160 airship has a range of 10,000km between refuelling stops (Global Security, 2005; Upham et al., 2003) (see Table 5.1).

“Precisely how much infrastructure is required to operate airships depends on the design of the airship. Some airships have been proposed with onboard docking systems which can be lowered to the ground, with the airship staying airborne for cargo transfers (Prentice et al., 2004). This would mean no infrastructure at all would be required on the ground to load and unload cargo. Other designs do require some infrastructure, however it is clear that airship take-off and landing facilities will be far smaller, and far cheaper, than for jet aircraft (ibid.).

“It is popularly believed that airships are peculiarly vulnerable to the weather. This is not the case. All methods of transport are affected by the weather. Airships, with their ability to move over land and sea, are well equipped to avoid extreme storms. “Airship vulnerability to weather extremes will likely be no greater, and probably less, than for conventional air transport” (Prentice et al., 2004). Furthermore, despite a few airship accidents around a century ago, with today’s engineering it is perfectly possible to make safe hydrogen-powered airships. It is also possible to use helium, which is inert.

“CargoLifter’s CL160 is designed to carry a cargo of 160 tonnes, whilst other companies (including HAV) say they can build airships which could carry cargos of 1,000 tonnes. This could result in significant economies of scale. There is at least one airship company which argues that very large airships could be built that could haul cargo at costs comparable to marine freight (Prentice et al., 2004).

“One problem linked to shifting air freight into airships is the fact that much air-freighted cargo is flown in the holds of passenger jets.However there would be some reduction in the fuel necessary for these planes as a result of the reduced weight. Additionally, about a third of air freight is carried in dedicated freight planes which airships could replace altogether (Civil Aviation Authority [CAA], 2009).

“Table 5.1 highlights the huge difference in emissions from long-haul aviation to HGVs. Airships could also in theory be used to replace HGVs for freight transport over shorter distances on land. As can be seen in Table 5.1, airships are more efficient than current HGVs. However, because they are less efficient than new HGVs, a modal shift from HGVs to airships is not recommended. For this application it would be better to shift to more efficient HGVs.”

Table 5.1 Estimate CO2 emissions for international freight
Mode CO2 emissions per freight-tonne-km
Current ong-haul aviation 0.6066kg (Defra)
Current HGVs 0.132kg (Defra)
New airships 0.121kg
New efficient HGV (40% saving) 0.079kg
Current maritime freight 0.013kg (Defra)

Estimated CO2 emissions by transport mode for international freight (2008) (freight-tonne-km).
Source: Based on figures from Upham et al. (2002) for airships and Defra data for long-haul aviation and HGVs.
Note that Upham refers to a specific plane, the Boeing 747, and Defra uses a generic long-haul figure.


The Zero Carbon Britain 2030 – A New Energy Strategy report is an interesting document and well worth reading.  Our blog Zero Carbon Britain 2030 provides an overview of the report’s content.

David M. Davison

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