The Economics of a Typical Recycling System
The economic analysis sketched here for basic research and engineering research applications is based on traceable data from at least one large facility and from a user survey conducted by the committee. For large systems, where liquid helium usage is at or above 50,000 liters (50 kL) per year, the costs scale approximately linearly to higher quantities primarily because the largest liquefiers now available are designed to handle about this level.
The one-time cost of installing such a liquefier in a research facility such as the National High Magnetic Field Laboratory, an NSF-funded example, is about $350,000. A fully integrated mechanical liquefier costs about $1,000,000, and cryogenic storage containers (dewars) cost about $70,000. These are nonrecurring costs. Overhead for an operator is about $100,000 per year. Maintenance, including the resupply of helium losses of 10 to 15 percent, is about $67,500 per year, and the cost of electricity is nearly $50,000 per year. The total capital outlay is thus $1,420,000, and operating costs are $217,500 per year. These expenses can be compared to the approximately $450,000 per year that it costs to simply buy and vent the same amount of liquid helium, using the average weighted cost to researchers of $9 per liter according to the survey conducted by committee member Moses Chan. This amounts to a saving of about $232,500 per 50 kL per year, giving a very favorable payback time of slightly over 6 years.
For smaller systems, several manufacturers sell small or medium-scale refrigeration systems know as lossless dewars, which are simply small stand-alone reliquifiers that are intended for a single low-temperature experimental station. For such systems, helium usage is reduced by an order of magnitude or more, with payback times
that are hard to intimate precisely but that are probably near the 6-year payback time of large systems.
This presents an obvious strategy for U.S. government-funded basic research requiring liquid helium. Consider a U.S. government grant where helium expenses are explicitly known. When such a grant is funded, the recipient could be presented with three choices: (1) a helium nonconservation charge would be assessed against the grant, reducing it by the difference between the actual requested amount and what the grant helium costs would have been had a helium conservation system been in place; (2) a plus-up to the grant if helium conservation was not in place but was planned for implementation in the first year of the grant such that the plus-up would cover some large fraction of the implementation cost; or (3) a grantee already conserving helium might get the full nonconserved budget for the project for a year or two as an incentive.