Pellet heating comes in two forms. You have the highly automated pellet stoves and boilers such as the ÖkoFEN units and you also have the none powered stoves. Both interest me and are important but for different reasons. Here is a video of someone who has designed a rocket stove to operate on wood pellets. A rocket stove is designed to run on small diameter fuel, pellets are not only small they have a high energy density. The rocket design is about making sure the draft of the fire chamber is as good as possible without using power assisted fans. That is why rocket stoves are so interesting, they achieve such a high efficiency even though there is no electrical fan involved. With a properly designed rocket heater you can also take advantage of one of the unique features of pellets, how they flow. As pellets have such a high density they flow well through hoppers, therefore its possible to create a none powered stove which can run for many hours with a full hopper of pellets. In the video you first see the design of the grate which will hold the pellets but will also let the ash through the grate so combustion is continuous. Next you see the various feed shoot designs. The later designs improve the spread of fuel over the grate and also provide a better flow of pellets from the hopper. It is interesting to see how much of a difference installing and removing the restrictor plate makes. The restrictor plate provides better air direction and also encourages more air to come in below the grate. Its also important to note that he recorded higher temperatures on the heat exchanger than with any wood he previously used. This is due to the high density of the pellets and their very low moisture content. The applications of these none/low powered stoves are for developing countries like India and the Oorja Stove. However they can also serve in developed countries as supplementary or back up heating. Another niche use could be to provide background heat for greenhouses and animal buildings.