2008 Progress Report: The Affordable Bioshelters Project: Testing Innovative Technologies, Working to Make High Performance Solar Greenhouses Cost Competitive

EPA Grant Number: SU833683
Title: The Affordable Bioshelters Project: Testing Innovative Technologies, Working to Make High Performance Solar Greenhouses Cost Competitive
Investigators: Raichle, Brian W. , Strauch, Yonatan
Institution: Appalachian State University
EPA Project Officer: Nolt-Helms, Cynthia
Phase: II
Project Period: August 31, 2007 through July 31, 2008
Project Period Covered by this Report: August 31, 2007 through August 30,2008
Project Amount: $75,000
RFA: P3 Awards: A National Student Design Competition for Sustainability Focusing on People, Prosperity and the Planet - Phase 2 (2007) Recipients Lists
Research Category: Pollution Prevention/Sustainable Development , P3 Challenge Area - Energy , P3 Awards , Sustainability


Much was accomplished during the first year (fall 2007 – spring 2008) of the Phase II Affordable Bioshelters Project grant, and some challenges arose. It is an appropriate time to reflect on lessons learned and to plan the next year’s activities. The purpose of this interim report is to communicate the progress so far and propose some adjustments to the scope and effort of the grant. A more detailed report will be submitted at the completion of the project.

Progress Summary:

The proposed work of the Affordable Bioshelters Project broke down into three prongs: 1) A long-term greenhouse performance study at the test site developed during Phase I; 2) Retrofit design and study; and 3) Liquid Foam Insulation Research and Development. Each of these areas is reported below.

Long-Term Greenhouse Performance Studies

A series of studies were conducted and became the subject of a master’s thesis by the project’s leading student Yonatan Strauch. The results show significant improvement in greenhouse thermal performance due to both subsoil heat storage and liquid foam insulation (LFI) technology as well as their combination. It was found that despite the ability of these systems to greatly increase nightly low temperatures, each technology has a great deal of potential for further optimization. For example, the foam was discovered to drop off in insulation value as it degraded, which emphasizes the need for the surfactant engineering already proposed. The subsoil heat storage system needs adjustment for optimization, though the data to inform this optimization process is still ongoing:  the key and interrelated influences of fan speed and soil-to-air temperature difference on energy exchange remain to be well understood. The reintroduction of moisture into the air at night was identified as a critical agricultural problem with sub-soil heat storage.

On the path to dissemination, the design and construction of the LFI system has provided much insight into foam generation, cavity sealing, and foam insulation analysis. This knowledge will be critical in the design of a prototype LFI greenhouse kit.

As per the partnership agreement with the farmer who hosted the experimental greenhouses, the greenhouses have now been transferred to the control of the farmer who is selling crops grown in them.

A number of physical assets, including greenhouse plastic, angle aluminum, and tools, will be used in the prototype construction proposed for the second year. The data acquisition system will made available to ASU’s Department of Technology for future student research projects.

Retrofit Design and Study

The subsoil heat storage retrofit was designed and installed. The design took into account lessons learned during Phase I, and used an extra layer of tubing to increase heating power, as well as a new kind of tubing which drains more fully so that less moisture is returned to the greenhouse.

Other technologies were considered for inclusion in the retrofit, but proved to be too problematic on a practical level to investigate at this point. The University of Manitoba, who developed an argon gas bag insulation system, recommended not perusing this technology due to problems they found in it. It was decided that the compost heat utilization system was too intensive to include in the scope of the retrofit, and would be better investigated independently.

The subsoil retrofit installation was challenging and yielded many lessons regarding how to best retrofit these systems. Different excavating tools and techniques were tried, including trenchers and various types of small excavators and tractors which could fit inside the greenhouse. It was concluded that a retrofitted system size should be limited by the extent of practical full excavation inside the greenhouse. This information was critical to providing recommendations to farmers interested in energy storage for their greenhouses.

A quantitative study of energy savings produced by the retrofit subsoil heat storage system was not undertaken due to the difficulty in controlling and quantifying all the necessary parameters. As this problem became apparent, steps were taken to preserve the financial resources invested in this study. Propane purchased for the experiment was sold to the owner of the farm. Equipment used at the retrofit site, including heaters, ventilation systems, and the data acquisition system, which represent over 60% of the investment in the site, will be used in the prototype construction proposed for fall 2008.

Before the site is decommissioned, it will be used in two experiments during summer 2008 that will address outstanding questions about sub-soil heat storage performance.

Liquid Foam Insulation (LFI) Research & Development

This prong has just begun. The design of the prototype liquid foam insulated greenhouse is in its early phases. Thermal conductivity characterization, originally proposed to be contracted out, will be performed at the newly constructed ASU Department of Technology’s wall section conductivity test cell.

The prototype design process will result in a kit that is easy to mass produce and easily assembled in a reasonable time with no special tools. It is hoped that this kit will shorten the time to widespread commercialization of LFI technology.

Additional Accomplishments in Relation to the P3 Program

The Affordable Bioshelters Project made a number of additional contributions that address the goals of the EPA P3 program. A team of graduate students learned to use the data acquisition and control software, LabView. In partnership with the ASU Department of Technology and another externally funded project, the Affordable Bioshelters Project purchased a 10 seat license of LabView software that will be made available to future student projects.

Many students were involved in the development of the initial test site as well as in the retrofit installation. Approximately two dozen undergraduate student volunteers benefitted from the hands-on learning that comes with executing a real life project. A small group of graduate students became more deeply involved in the execution and leadership of the project, completing portions of the project for class requirements.

Community partnerships have been established. Watauga Rivers Farm, in Valle Crucis, NC, hosted the Phase I test site, and now operates the three greenhouses constructed there. Lily Patch Farms, in Sugar Grove, NC, site of the retrofit research, has expressed an interest in a sustainable farming and renewable energy research partnership with the university. The partnership with the University of Manitoba’s Biosystems Engineering has led to the successful installation and study of a subsoil heat storage system in a much colder climate. The proposed prototype greenhouse will likely be the first tenant at the Watauga County EcoPark. This greenhouse will then be used for a P3 Phase I algae-for-biofuels project as well as aquaculture research.

Project Summary and Status

It has been concluded that subsoil heat storage adoption can be most effectively promoted by providing growers with clear and accurate information about the systems. Because greenhouse growers are geographically dispersed and the systems are relatively straightforward to install, a “subsoil heat storage system installer” is likely not a viable profession. Instead, growers, who usually have all the skills and tools needed to install a system themselves, can benefit from realistic performance and cost savings estimates to help them make informed decisions and form practical guidelines that describe design, materials, and installation best-practices.

Valuable experience was gained in retrofitting an existing greenhouse with a subsoil heat storage system. However, the energy saving capability of the system was not quantified. In order to meet the goals of this prong, the system will be quantified in terms of energy exchange in a matrix of varied airflow and soil-to-air temperature differences, and in terms of moisture return at night.

Liquid foam insulation is quite effective at reducing greenhouse heat loss at night. However, it is not a candidate for a do-it-yourself project. It is a specialized technology, which is relatively complex to design, install, and operate. Adoption can be best promoted by providing growers a predesigned kit they could purchase and self assemble.

Relevant Websites:

Phase 1 Abstract
Phase 1 Final Report

Progress and Final Reports:

Original Abstract
  • Final

  • P3 Phase I:

    The Affordable Bioshelters Project: Testing Innovative Technologies, Working to Make High Performance Solar Greenhouses Cost Competitive  | Final Report