Zero-emission by low cost construction method of geothermal heat collection

SHIN NIPPON AIR TECHNOLOGIES CO., LTD.

Fig.1 Geothermal Tornado Method

Outline

Geothermal heat, the one of renewable energy, has the following advantages and disadvantage in terms of environmental aspects.

(Advantages)

1. It is possible to use the air heat source heat pump even in an environment where the outside temperature is below freezing.

2. There is no outdoor unit to exchange and release the heat to outdoors, and its operation noise will be extremely low.

3. There is no impact to the environmental pollution because the feature of geothermal heat exchanger is closed-type.

4. There is no heat release to outside air during cooling and heating, it will be unlikely to cause the heat island phenomenon.

(Disadvantage)

1. The initial cost of the system (digging well cost etc.) will be high thus its cost recovery period becomes long.

To spread the geothermal heat utilization, we have developed a new construction method to reduce the initial cost of the system, and have been adopted in two buildings since the market introduction in 2017. From these things, we intend to promote its further spread and lead the expansion of renewable energy usage.

Description

１．Achievement goals (development, commercialization, cost, penetration rate, etc.)

(1) Geothermal heat, at a depth of 10 meters or more from the ground surface, is constant throughout the year and can be used effectively as an air conditioning heat source. The current mainstream of heat collection method is to insert a heat collecting U-tube after drilling a hole with a depth of 100 to 150 meters, which requires double construction and specialized workers for hole drilling and the U-tube insertion work. This initial cost recovery period will be from 14 to 20 years.

(2) As a countermeasure for this issue, we have developed a new method of installing a double spiral heat collecting tube (Double spiral tube®) in a compressed state inside of the foundation pile pre-fabricated at the factory when the building is newly installed, and extending the tube at the same time as the pile construction on site (Fig. 1 "Geothermal Tornado Method ®"). This method does not require two workers for excavation and heat collection pipe construction work and heat collection pipe installation work, so it aims to recover its cost within 8 years.

２．Tasks to be overcome for achieving the Challenge

(1) It is necessary to develop contractors to maintain the construction quality and to spread it, in order to expand this method widely with improvement its awareness.

(2) It is necessary to evaluate the heat collection of this method by using the actual operation data of the Double spiral tube®, and to provide the necessary information to easily study the heat source system in the new building plan.

３．Specific action of our company

(1) It is planned to form a consortium of this method with the partner, and to improve the construction quality and develop human resources by disclosing the technologies to the participating companies. In addition, a load test is being carried out in order to obtain the Minister's accreditation in Japan for this method (structural method with installation of the Double spiral tube®).

(2) While accumulating the verification results on the cost aspects of this method and the effectiveness of heat sources, it is planned to make proposals to relevant parties to apply the subsidy system when adopting this method to promote the introduction of geothermal heat.

４．Effect of reducing greenhouse gas when the Challenge is achieved, etc.

(1) It has been reported that the introduction of the geothermal heat pump system in non-residential buildings has been changing around the several dozen to 100 cases in recent years, and also disclosed that the amount of CO2　emissions can be reduced by 25% compared to air source heat pump system (according to the geothermal heat utilization pamphlet, Ministry of the Environment 2019), and recognition of geothermal heat is moving ahead.

(2) As the ratio of air conditioning heat source equipment to the electricity consumption of office building is approximately 28% (Characteristic of energy consumption of office building; refer to Energy Conservation Center, Japan HP), the expansion of geothermal heat utilization, combined with introduction of high efficiency equipment etc., will contribute to execute "Strategic Energy Plan" (to achieve the net zero energy building (ZEB) with regard to for all newly constructed buildings on average by 2030, which was determined by the Cabinet Decision in April 2014) .