Extra credit What utility rate structure makes building ther

Extra credit: What utility rate structure makes building thermal energy storage economical? What are two ways implementing building thermal energy storage? How do you move quickly to previous window on a computer?

Solution

(A) The buildings sector accounts for about 76% of electricity use and 40% of all U. S. primary energy use and associated greenhouse gas (GHG) emissions, making it essential to reduce energy consumption in buildings in order to meet national energy and environmental challenges (Chapter 1) and to reduce costs to building owners and tenants. Opportunities for improved efficiency are enormous. By 2030, building energy use could be cut more than 20% using technologies known to be cost effective today and by more than 35% if research goals are met. Much higher savings are technically possible.

Building efficiency must be considered as improving the performance of a complex system designed to provide occupants with a comfortable, safe, and attractive living and work environment. This requires superior architecture and engineering designs, quality construction practices, and intelligent operation of the structures. Increasingly, operations will include integration with sophisticated electric utility grids.

The major areas of energy consumption in buildings are heating, ventilation, and air conditioning—35% of total building energy; lighting—11%; major appliances (water heating, refrigerators and freezers, dryers)—18% with the remaining 36% in miscellaneous areas including electronics. In each case there are opportunities both for improving the performance of system components (e.g., improving the efficiency of lighting devices) and improving the way they are controlled as a part of integrated building systems (e.g., sensors that adjust light levels to occupancy and daylight).

Key research opportunities include the following:

(B) Thermal energy storage through PCM is capable of storing and releasing large amounts of energy. The system depends on the shift in phase of the material for holding and releasing the energy. For instance, processes such as melting, solidifying or evaporation require energy. Heat is absorbed or released when the material changes from solid to liquid and vice versa. Therefore, PCMs readily and predictably change their phase with a certain input of energy and release this energy at a later time.

PCM depends on latent heat storage. Compared to the storage of sensible heat, there is no temperature change in the storage. In a sense every material is a phase change material, because at certain combinations of pressure and temperature every material can change its aggregate state (solid, liquid, gaseous). In a change of aggregate state, a large amount of energy, the so-called latent heat can be stored or released at an almost constant temperature. Thus a small difference in temperature can be used for storing energy and releasing the stored energy.

Feasibility of technology and operational necessities top:

The application of PCMs in buildings can have two different goals (Pasupathy, Velraj & Seeniraj, 2008). First, the PCMs can be used to utilize natural heat and cold sources. For instance, solar energy for heating during the evening/night or the use of night cold for cooling during the day. Second, PCMs can use manmade heat or cold sources.

In addition, different ways of using PCMs are available. In buildings, these again fall into two groups. PCMs can be located in building components such as walls or ceilings, or can be arranged in separate heat or cold stores. Using PCMs within buildings components are generally passive systems. The heat or cold is stored automatically and released when indoor or outdoor temperatures rise or fall beyond the phase change point of the material. Using PCMs in seperate heat or cold stores are usually based on active systems. The stored heat or cold is in containment seperated from the building itself and heat or cold transfer is not automatic, but used on demand.

(C) There are several ways to switch between open windows. Many users reach for the mouse, point to the Taskbar, and then click the button for the window they want to bring to the foreground. That\'s about the slowest, least convenient method.

If you\'re a fan of keyboard shortcuts, like I am, you probably use Alt-Tab to cycle between open windows. That\'s a better method, but Windows uses such tiny thumbnails, I often find myself squinting to see if the selected window is the one I\'m after--and sometimes I actually end up with the wrong one.

Windows Vista and 7 users can also press Win-Tab to engage Flip View, a kind of Rolodex-style window selector. This should be the best option, as it uses much larger, easier-to-view thumbnails (a term that really doesn\'t apply here). But for whatever reason, I don\'t like it.

No, for my money, the fastest and most effective way to cycle between open windows is by tapping Alt-Esc. Doing so instantly switches you to the next open window, then the next after that, and so on. There\'s no interim step, no thumbnail view to squint at or cycle through. Tap once and bam: the next window appears. Not the one you want? Tap again and bam: next window.