Control Recommendations for Emerging Residential Renewable Energy Systems

Open Access
Author:
Carbonnier, Kevin Mike
Graduate Program:
Architectural Engineering
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
June 11, 2014
Committee Members:
  • Stephen James Treado, Dissertation Advisor
  • Stephen James Treado, Committee Chair
  • Jelena Srebric, Committee Member
  • Jeffrey Brownson, Committee Member
  • Susan W Stewart, Committee Member
Keywords:
  • Solar thermal
  • MATLAB
  • Simulation
  • Set Points
  • Renewable Energy
  • Combisystem
  • Building Model
  • PI Control
  • Controls
Abstract:
As solar hot water collectors are becoming more affordable in the residential sector, properly understanding the system dynamics to better configure and control the energy systems of buildings is of utmost importance. Innovative solar storage tanks that have two internal heat exchange coils can improve performance and reduce energy consumption in mechanical systems that employ a hydronic space heating system. The purpose of this project is to develop a Matlab model of one such system found at the MorningStar solar home at the Pennsylvania State University campus. Because the solar storage tank is a complex system involving three simultaneous energy exchanges, the model is necessary to evaluate the potential benefits and understand the dynamics of the novel storage tank. With the developed model, simulations are run to evaluate the net daily energy balance of the building with the grid, as well as the occupant comfort levels for several heating season days. The simulations explore the effects of cloud cover, time of year, temperature and flow rate set points for the radiant floor heating system, and flow rate through the solar hot water collector. These simulations are run for several mechanical system designs in order to broaden the applicability of the results and to demonstrate the flexibility of the developed code. Several conclusions are drawn from the simulation results, including recommendations for set points and suggestions for optimal system configuration when using a dual heat exchanger solar storage tank coupled with a hydronic heating system and a solar hot water collector. First, supplying the coolest possibly temperature into the radiant floor heating system allows for the greatest solar thermal energy generation, which improves the overall performance of the system, although determining this minimum temperature is not intuitive and can be solved with the aid of simulations. Second, routing either the domestic hot water system or the space heating system, whichever of the two has the least efficient backup heating system, through the bulk of the solar storage tank may allow for greater energy use reduction, depending on the time of year, solar availability, and system set points.