Editing Stirling engine (section)

=== 20th-century revival ===
[[File:Philips Stirling engine.JPG|thumb|Philips MP1002CA Stirling generator of 1951]]

During the early part of the 20th century, the role of the Stirling engine as a "domestic motor"<ref name="Finkelstein-2001-34" /> was gradually taken over by [[electric motor]]s and small [[internal combustion engine]]s. By the late 1930s, it was largely forgotten, only produced for toys and a few small ventilating fans.<ref name="Finkelstein-2001-55" />

====Philips MP1002CA====
Around that time, [[Philips]] was seeking to expand sales of its radios into parts of the world where grid electricity and batteries were not consistently available. Philips' management decided that offering a low-power portable generator would facilitate such sales and asked a group of engineers at the company's research lab in [[Eindhoven]] to evaluate alternative ways of achieving this aim. After a systematic comparison of various [[prime mover (locomotive)|prime movers]], the team decided to go forward with the Stirling engine, citing its quiet operation (both audibly and in terms of radio interference) and ability to run on a variety of heat sources (common lamp oil&nbsp;– "cheap and available everywhere"&nbsp;– was favored).<ref name="Hargreaves-1991-28-30" /> They were also aware that, unlike steam and internal combustion engines, virtually no serious development work had been carried out on the Stirling engine for many years and asserted that modern materials and know-how should enable great improvements.<ref name="Philips-1947" />

By 1951, the 180/200 W generator set designated MP1002CA (known as the "Bungalow set") was ready for production and an initial batch of 250 was planned, but soon it became clear that they could not be made at a competitive price. Additionally, the advent of transistor radios and their much lower power requirements meant that the original reason for the set was disappearing. Approximately 150 of these sets were eventually produced.<ref name="Hargreaves-1991-61" /> Some found their way into university and college engineering departments around the world, giving generations of students a valuable introduction to the Stirling engine; a letter dated March 1961 from Research and Control Instruments Ltd. London WC1 to North Devon Technical College, offering "remaining stocks... to institutions such as yourselves... at a special price of £75 net".{{citation needed|date=July 2020}}

In parallel with the Bungalow set, Philips developed experimental Stirling engines for a wide variety of applications and continued to work in the field until the late 1970s, but only achieved commercial success with the "reversed Stirling engine" [[Applications of the Stirling engine#Stirling cryocoolers|cryocooler]]. They filed a large number of patents and amassed a wealth of information which they licensed to other companies and which formed the basis of much of the development work in the modern era.<ref name="Hargreaves-1991-77" />

====Submarine use====
In 1996, the Swedish navy commissioned three [[Gotland-class submarine]]s. On the surface, these boats are propelled by marine diesel engines; however, when submerged they use a Stirling-driven generator developed by Swedish shipbuilder [[Kockums]] to recharge batteries and provide electrical power for propulsion.<ref name="Kockums" /> A supply of liquid oxygen is carried to support burning of diesel fuel to power the engine. Stirling engines are also fitted to Swedish [[Södermanland-class submarine]]s, the [[Archer-class submarine]]s in service in Singapore, and the Japanese [[Sōryū-class submarine]]s, with the engines license-built by [[Kawasaki Heavy Industries]]. In a submarine application, the Stirling engine offers the advantage of being exceptionally quiet when running.{{citation needed|date=July 2020}}