Thermoelectric Generators for Well Head Production Facilities

Abstract

Abstract The Thermoelectric Generator (TEG), first implemented by NASA in the 1960s to power its instruments on deep space missions, has received renewed interest in oil & gas production facilities at remote, unmanned and off-grid wellhead sites. Such TEG power generators feature all solid-state components with no moving parts which result in long life power units that operate under all weather. It also has long operating cycles between maintenance due to the simple internal design of a Thermoelectric Generator (TEG). Power thermocouples inside a TEG convert heat directly into electricity, and this enables them to work 24 hours a day with no moving parts and without battery backup. Availability of a stable and very low maintenance power generator is now a pre-requisite for off-grid and unmanned well head sites that have numerous critical instruments , electrically powered safety systems, in addition to powering the cathodic protection needed for casing pipe integrity. Important criteria for selecting a low maintenance power generator at remote sites are examined, and a comparison is made between different off-grid power generation technologies used for critical loads in production. The basic physical concept governing TEG operation, known as the Seebeck Effect, is explained along with the fundamental equation governing thermoelectric power output. Sources for heat input, using associated gas or other fuels, and typical TEG power unit construction are detailed and compared to the criteria for reliable power production at wellhead sites. TEG use cases for production facilities will be highlighted. Site layouts of the TEG units and criteria for placing them near well heads are explained. Hybrid Solar-TEG approaches for adding renewable energy features to the Thermoelectric principle will be detailed. Introduction This paper outlines the application of the Thermoelectric Generator (TEG) to the reliable electrical power generation requirements of Off-Grid, Remote and Unmanned Oil & Gas Wellheads. Typical power demands for such sites at, both onshore and offshore production facilities range from 100 Watts to 5000 Watts per wellhead site. Current power generation techniques are either based on renewable energy, which is dependable on unpredictable weather and environmental conditions, or rotating equipment which have many moving parts requiring regular maintenance. Thermoelectric Generators (TEGs) are all-weather power generators that work continuously with while having no moving parts, thus are suitable for reliably powering wellhead sites. A major difference to conventional heat-engine type power generators is that TEGs have solid state power units, completely noise-free and low profile. Due to their solid-state power unit and very low maintenance requirements, they can be applied to any remote and off-grid site where 24hr per day power generation under all weather conditions is required. This characteristic eliminates the requirement of energy storage, such as batteries, due to weather and the daily solar cycle, thus presenting an added advantage. A TEG converts heat directly into DC electricity. As heat moves from a low pressure gas burner through a thermoelectric module, it causes an electrical current to flow. Since it is a direct conversion from heat into electricity, then are there no moving parts in the device. The small amount of gas required for the TEG operation can be either from the oil wellhead’s associated gas or from the gas wellheads. Heavier LPG fuel can also be used in tanks to reliably fuel the TEGs for a long term, which is typically continuous operation for many months, depending on tank size and fuel consumption rate.