EME 811
Solar Thermal Energy for Utilities and Industry

7.1. Active versus Passive


D&B Chapters 13 and 14 cover the two types of district heating; active and passive.

The difference between those types is rather simple. The active heating implies using specially designed solar collectors that are installed on the building and supply energy to partially of wholly satify the building energy loads. The passive heating means that building itself acts as a solar collector, and hence the properties of building materials and building design both play role in the energy balance of the system.

The typical basic components of an active solar heating system include:

  • collector,
  • storage unit
  • load
  • auxiliary source

Design approach is similar for both air and water heating systems, but the storage types and equipment are different. When such standard designs are applied to specific building cases, a number of key parameters are manipulated to ensure that the thermal performance of the system meets the space heating requirements. Please refer to the following reading for more details on active solar heating.

Reading assignment

Book chapter: Duffie, J.A. Beckman, W., Solar Engineering of Thermal Processes, Chapter 13:

-- Sections 13.1-13.3  -- These sections present the basic information on how the solar heating systems are designed. It provides schematics and tables of design parameters that regulate the thermal performance. Study both types of designs  - with air and water as heat transfer fluids.

-- Section 13.5 -- This section presents an example of computed design for a specific residence area and shows some parameter matching and performance data for this case.

-- Section 13.8 -- This section describes the concept of seasonal energy storage

Passive solar heating uses quite different design strategies since it involves building elements rather than regular collectors. Passive solar has been around for millennia and is considered the low hanging fruit, so to speak; however, it requires careful design and is often difficult to implement in a retrofit scenario. Thus, a medium commercial building in an urban setting would have very limited options for renovation at reasonable cost toward a passive heating solution. At the same time, if you are designing a new building, the entire façade, orientation, and structure of the building can be leveraged to maximize solar utility passively through awnings, placement of thermal mass, rotation of the building, and more. Although most of the lessons in this course focus on active solar thermal energy conversion, we should not underestimate the impact of passive solar heating methods. While some passive heating methods can be cumbersome or may require some user input to keep costs down (e.g., movable shade elements), the thermal comfort of a space and the subsequent heating costs can be greatly impacted by careful design and the effective use of passive solar thermal energy conversion techniques. In this course the passive techniques are reviewed only briefly.

Reading assignment

Book chapter: Duffie, J.A. Beckman, W., Solar Engineering of Thermal Processes, Chapter 14: Sections 14.1-14.3

Website: Drake Landing Solar Community (DLSC), Okotoks, Alberta (Canada), URL: http://www.dlsc.ca/

This website contains information about the solar community in Canada, which implements a range of solar technologies to cover 90% of their space heating needs. The website contains description of features and technologies, and under 'Publications', you will find a number of bi-annual reports showing performance and meteo data from different periods of DLSC operation.

Supplemental reading: 

Duffie, J.A. Beckman, W., Solar Engineering of Thermal Processes, Chapter 14. 

Read the rest of Chapter 14 of the textbook if you are interested to learn about various passive technologies and how they are assessed.