The crop dryer will be required for curing your onions in storage. We have been using the Caldwell heater for many years. The heater can be supplied with either a centrifugal or axial fan. When noise is an issue, the centrifugal is your best option. To make sure your heater is in working order before the season, the proper yearly maintenance is required, since certain parts wear out and should be replaced.
By law, you need to have the dryer outside the building, which means it heats up fresh air to feed to the storage. The heater will be installed with an upstream fan and downstream duct & damper. There are certain restrictions when installing a heater for your storage; certain distances are required from combustibles. Ask Dayson for advice, since regulations tend to change.
Here is more information about Crop Dryers from Dayson Agricultural Ventilation.