To design, and then to maintain

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Planning for the maintenance of an engineering structure as an integral part of its design has become routine in modern practice. Yet, by necessity, this preoccupation was also present in numerous ancient projects. For example planning of the irrigation system of Sechuan, with its intake at Dujiangyang, obviously took into account the need to clean the intakes and to maintain the dikes and the intake control mechanisms. The designers also anticipate the need for a procedure to dewater the works for maintenance during low-flow periods. Canal cleaning was a continuous activity in the old land of Sumer. From the archives of Mari, we know that these maintenance efforts were tedious and

Table 10.1 The oldest known dams

Name

Region

Probable

Date

Ht.

(m)

Len.

(m)

Type

Water­

Course

Purpose

Jawa

Djebel el-

Arab

(Jordan)

3000 BC or earlier

5.5

80

Fill between stone walls (Fig 2.5)

Derivation canal from the wadi Rajil

Floodwater storage (Fig 2.7). The oldest known dam.

Khirbet el – Umbashi

Djebel el – Arab (Syria)

3000 BC

7

40

Earth dam

Wadi el – Umbashi

Reservoir in the bed of the wadi itself (Fig 2.8)

Sadd el – Kafara

Egypt(near Memphis)

2650 BC

14

113

Fill between two rock faces

Wadi

Garawi

Protection against floods of the wadi Garawi. The first known large dam (Fig 3.3, 3.3a)

Weir of Khanouqa

Middle

Euphrates

(Syria)

1800 BC?

Rocks (uncut basalt blocks)

Euphrates

Weir on the Euphrates, headworks of the “Semiramis canal” (Fig 2.13)

Boedria

Copai’de

(Greece)

1300 BC

2

1250

Fill between two walls

Kephissos

Reservoir (Fig 4.6). See other dams, table 4.1

Kofini

Tiryns

(Greece)

1200 BC

10

100

Fill between two rock walls

Lakissa

Rerouting of a river, flood protection (Fig 4.12, 4.13)

Lake Rusa (north)

Urartu

(Armenia)

720 BC

15

75

?

Lake Rusa

Reservoir: lake Rusa (Fig 2.18). In service until 1861 AD, then rebuilt in 1952.

Lake Rusa (south)

Urartu

(Armenia)

720 BC

7

60

?

Lake Rusa

Reservoir; lake Rusa (Fig 2.18)

Weir of Ajileh

Assyria

(Iraq)

694 BC

3

230

Large blocks of cut stone

Khosr

Weir on the Khosr, headworks of a deri­vation canal of the Khosr to Nineveh

Bavian

Assyria

(Iraq)

690 BC

?

?

Gomel

Weir on the Gomel, headworks of the Sennacherib canal

Shaobei, or Anfengtang

Anhui

(China)

585 BC

11

Earth, straw and wooden stakes

Tributaries of the Huai

Reservoir; still in service today

Maryab

Yemen

510 BC

15

650

Earthen dike, rock protection

Wadi

Dhana

Intake works for two canals conveying flood waters of the wadi (Fig 3.12). Breached in the 7th century AD.

Panda

Sri Lanka (Ceylon)

370 BC

7

2,600

Earthen dike

Seasonal reservoir

Bassawak,

Tissa

Sri Lanka (Ceylon)

300 BC

8

1,800

3,300

Earthen dikes

Reservoirs (Fig 7.3)

Paskanda

Sri Lanka (Ceylon)

300 BC

17

?

Earthen dike

Seasonal reservoir

Mala’a

(lake

Moeris)

Fayoum

(Egypt)

250 BC

7

8,000

Masonry

Joseph

canal

Reservoir (lake Moeris) fed by flood – waters of the Nile (Fig 3.6). In use until the 18th century AD.

N. B. Two other dams, whose conditions were known in the Roman period, are candidates for being even older: the dam of the wadi el-Souab, a possible headworks on an irrigation canal of the ancient Mari (Fig 2.11), and the dam of the lake of Homs (Fig 6.33).

sometimes difficult. The ports of Pylos in the IIIrd millennium BC, and the port of Rome built by Trajan, are examples of projects designed from the beginning to use the flow of the river to keep the entrances open. Of course any project subject to sediment deposition or erosion can quickly be rendered useless due to lack of maintenance. This is why the reclaimed land of Mesopotamia lapsed back into desert so quickly after the Mongol invasions of the 13th century. Another example is that marshes quickly reap­pear as soon as the Etruscan know-how in lowland drainage is lost in Italy.

The early technologies

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One may be skeptical of the overall contribution of Hellenistic science – its relative dis­connection with practical application, or its failure to document the significant revolu­tion represented by hydraulic energy. But the incontestable fact remains that in the study of the science and techniques of Antiquity preceding the Middle Ages, one cannot avoid marking pre – and post-Alexandria. The Hellenistic period represents a watershed, or divide, that is reflected in the two distinct parts of this book.

The earliest technology appeared before the turmoil that followed the epic reign of Alexander the Great. The elements of this technology can be briefly listed in the order of their appearance as follows:

– dams, made of rocks or earth, whose earliest traces are found on the Syro – Mesopotamian steppes at the end of the IVth millennium BC (Jawa, Khirbet el – Umbashi); the characteristics of the oldest of these dams are summarized in Table 10.1.

– derivation canals, sometimes created through cut-and-fill on the floodplain, with gates and guide vanes of stone; the oldest of the major works of this kind are proba­bly those in the ancient land of Sumer, in the IVth millennium BC, but the genesis of this technology really belongs to all of the fertile crescent.

– drainage facilities, sewer systems of stone, bricks, or clay; we have seen them in the ancient cities of the Indus, in Sumerian settlements; they are particularly prominent in Crete.

– navigation canals, necessary adjuncts of the cities of lower Mesopotamia, for each Sumerian city has its own port; on the middle Euphrates, the Semiramis canal and the nahr Daourin are surely the oldest; in China, from the 5th century BC, the Hong canal connects the basins of the Yellow River to those of the Yangtze;

– the sailing vessel, first appearing in the Persian gulf, then in Egypt and the Aegean Sea;

– water supply systems, whose technology seems to first appear in Minoan Crete;

– and, somewhat of a special case since it is really an evolutionary technique that is conceived during the iron age: the qanats.

From the great cauldron of ideas that was Alexandria emerged the principles of hydrostatics, and the fundamental understanding of the effects of pressure. The inverse siphon and the pressure conduit are used in water supply systems. And hydraulic ener­gy makes its appearance in the form of the watermill and the noria, two systems destined to see considerable development in the Middle Ages – the noria in the East and Far East, the water mill everywhere. The blossoming of hydraulic technology in the Middle Ages is seen in the mills dotting the landscape from the Atlantic to the Sea of Japan. Later, we can credit the Persians with the idea of the windmill, and the Chinese with the axial rudder and modern sail, as well as the navigation lock.

Ladders

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Inappropriate use of ladders is the number one cause of falls. Ladders are used so often in framing that it is easy to overlook basic safety guidelines. Always remember the following:

• The feet of the ladder need to be on a stable surface so the ladder will be level.

• When ladders are used to access an upper surface, make sure they extend at least three feet above the upper surface, and secure the top to prevent them from being knocked over. (See “Ladder Extension" photo.)

• Do not use the top or top step of a step ladder.

• For straight or extension ladders, remember the 4 to 1 rule. For every four feet of height the ladder extends, it needs to be placed one foot out at the base.

• Check the ladder for defective parts, and remove any oil or grease on the steps.

• Never leave tools on the top step of a ladder.

Use common sense. If you are not sure that a ladder is safe, don’t use it.

Fall Protection

OSHA provides that for unprotected sides and edges on walking or working surfaces, or for leading edges of six feet or more, framers must be protected from falls by the use of a guardrail system, a safety net system, or a personal fall arrest system. For leading edge work, if it can be demonstrated that these systems are not feasible or they create a greater hazard, then a plan may be developed and implemented to meet certain OSHA requirements.

Most deaths in the construction industry happen as a result of falls. Falls also cause many of the injuries that occur on the job site, according to OSHA.

Because framing can place you a story or more off the ground, it’s important to work safely and to become aware of fall protection equipment, as well as systems (such as guardrails, safety nets, and covers) that can help prevent falls.

The following sections cover safety tips on equipment and systems. Using these can help protect yourself and others on the job site from falls.

The most commonly used fall protection systems in framing are the personal fall arrest system and the guardrail system. The guardrail system works well for a large flat deck. The fall arrest is better suited for pitched roofs.

Guardrails

Metal guardrail supports can be nailed to the outside of walls to support 2 x 4 railings. However, it is more common to see railing made out of 2 x 4 for the support and railings. These railings can be nailed on before the walls are raised. Following are some OSHA regulations on guardrails:

• The top edge of the top rail must be at least 42" (plus or minus 3") above the working level.

• Mid-rails must be installed at a height midway between the top edge of the top rail and the working level.

• The top edge of the guardrail system must be able to withstand 200 pounds applied within two square feet in an outward or downward direction.

• The mid-rail must be able to withstand at least 150 pounds in an outward or downward direction.

• When access is provided in the guardrail system, a chain, gate, or removable guardrail sections should be placed across the opening when loading operations are not taking place.

Personal Fall Arrest Systems

These systems typically consist of a full body harness, a lanyard, a lifeline, and an anchor. (See “Fall Arrest System" photo.) Each of these parts is available in many different types. Some of the OSHA regulations for these systems are listed below.

• D-rings, snaphooks, and carabiners must have a minimum tensile strength of 5,000 pounds.

• Lanyards and vertical lifelines must have a minimum breaking strength of 5,000 pounds.

• Anchors must be capable of supporting at least 5,000 pounds per framer.

• The system must be rigged so that the framer cannot free-fall more than 6 feet.

• The attachment point for a body harness is to be located in the center of the wearer’s back near the shoulder level or above the wearer’s head.

If you have new framers who are not used to working with fall arrest systems, you will need to spend some time with them to help them become familiar and comfortable with this equipment.

Fall arrest system

Rebates and Tax Breaks Could Be the Keys to the Future

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What takes the sting out of the high cost of buying into renewable-energy systems is a combination of federal tax credits and state and utility rebates. The federal credit, pegged at 30% of system cost, is open to

Rebates and Tax Breaks Could Be the Keys to the Future
Rebates and Tax Breaks Could Be the Keys to the Future
Подпись: DC pump
Подпись: Controller

everyone. State and utility rebates, however, vary. Where they are generous, such as in California or Hawaii, you can expect robust growth for the solar industry.

Originally due to lapse in 2008, the fed­eral tax credit has been extended for eight years. However, the on-and-off nature of government support is a "travesty," says Collins, and a chronic problem for the solar industry. "You can’t do this with stops and starts," he adds. "It’s been the history of incentives for renewables for the past 25 years."

Merrigan says that as many as 35% of all houses in Hawaii have solar water-heating systems, in part because of generous rebates. "I think it’s key," he says. "It’s just like for photovoltaics. PV is growing where there are incentives. The first cost of the system can
be enough to make people think about it, but to not want to make that investment.

If you have incentives that can bring down that first cost, you see good market penetration."

Still, credits and incentives are available now, and they make a much bigger differ­ence proportionally for hot water than for photovoltaic systems. "You displace roughly 2kw of energy with your water system, so it’s like putting a 2kw PV system on your roof," says Collins. "But it’s hot water. A 2kw sys­tem of PV might be $20,000, but a 2kw solar hot-water system might be $6000. I’ve often said that solar hot water is the most misun­derstood bargain out there."

Rebates and Tax Breaks Could Be the Keys to the FutureScott Gibson, a contributing editor to Fine Homebuilding, lives in East Waterboro, Maine.

Seasonal Variation in Pavement Design and Analysis – Some National Examples

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A.1 Introduction

The primary objective of this annex is to present examples of how moisture condi­tion is taken into account in pavement design and analysis.

The pavement design regarding the influence of water has significantly different objectives in different European countries. While in central and northern Europe the most important question is how to protect the pavement structure from frost action, in southern European countries it is more critical to control excessive water that suddenly penetrates the pavement after heavy rainfall. At the same time identical processes play significantly different roles in different climates. For example, the suction, that has negative effect in locations of freezing and thawing, has positive effect in southern countries by increasing the stiffness, and this influences the de­cision of which type of material is used in unbound base and sub-base. In northern countries the percentage of fines is limited typically to 5-8%, while the Mediter­ranean countries allow up to 15% fines.

In many parts of Europe freeze/thaw effects play a crucial role in pavement de­sign. How these effects are taken into account in pavement design varies in complex­ity from using the frost index, or Stefan or modified Berggren equations (Aldrich & Paynter, 1956) to calculate frost depth to coupled heat/moisture flow models. Most of the European pavement design methods take into account phenomena related to freezing and thawing by using the frost index. This indicator is supposed to account for the “quantity of frost” to which a pavement was subjected for a given period. The frost depth is then calculated based on some empirical equation as a function of frost index. Some pavement design methods also consider the influence of sunshine on this phenomenon.

Many design methods take into account the loss of bearing capacity during thaw­ing. This is typically done by adjusting the modulus of each of the unbound mate­rials by a reduction factor that depends on the frost susceptibility of the material (COST 337, 2002).

The European project AMADEUS (Amadeus, 2000) identified the need for further research of deterioration mechanisms related to freezing and thawing and development of a long-term predictive model for freeze/thaw related deterioration.

The project also identified the need for more information on how the bearing capac­ity of different types of soils is affected by the drainage conditions.

The World Bank’s Highway Development and Management Model HDM-4 (ND Lea International, 1995) models the seasonal performance variation using a simple two season model (“wet” and “dry” seasons). The program uses the follow­ing parameters:

• mean monthly precipitation,

• drainage effectiveness,

• surface cracking,

• potholed area,

to calculate the ratio between “wet” and “dry” pavement adjusted structural num­bers. Loizos et al. (2002) modified this approach in the Road Infrastructure Man­agement System (RIMS) developed for the Greek government, to enable multiple season analysis, more suitable to a European context, by introducing the environ­mental function.

In the following, examples of how seasonal variations are handled in design sys­tems are given.

A.2 Finland

In Finland the design and analysis of pavement structures is done by separate con­sideration of different criteria:

• Frost resistance (structure and subgrade)

• Traffic loading/Resistance to fatigue

• Resistance to settlement (deformation in structural layers and subgrade)

• Rutting due to studded tyres

A.2.1 Frost Design

Design of public roads in Finland still, commonly, uses a semi-empirical method based on acceptable calculated frost heave, which depends on

• road class;

• structural durability;

• how homogenous the subgrade is;

• the freezing index, F10, of the geographical location (583-1416 °C. days); and on

• an empirical factor of frost heave of the subgrade, which depends on the pro­portion of soil passing the 63 ^m and 2 mm sieves and whether it is a wet/dry location.

On homogenous clay soil, the measured frost heave values can also be used.

According to the results of the “Road Structures Research Programme” the con­trol of frost behaviour of the road is divided into two parts: control of frost heave and control of the effects of thaw weakening. The frost heave of a road is estimated using the segregation potential (SP) concept, in which SP is the parameter that describes the frost susceptibility of the subgrade. The total thickness of the road structure is designed on the basis of frost susceptibility of the natural subgrade, and on the thermal conductivity of the used materials. If necessary, the structure is protected using insulation against frost, so that the permitted frost heave, set as the design criterion, is not exceeded. The procedure can be applied in designing new roads and improving old roads in all road classes. The program also calculates settlement pro­files based on the investigations and identification of variations in the water content of soil layers along the road line.

Steps in Construction of FAST Diagrams

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The following steps are recommended in the construction of the FAST diagram:

1. Function listing. Prepare a list of all functions, by assembly or by system, using the verb-and-noun technique of identification of function. Do this by brainstorming the questions (a) “What does it do?” and (b) “What must it do?”

2. The function worksheet. Using lined paper, prepare a three-column function work­sheet in the format shown in Fig. 10.2. Insert the listed functions from above, one at a time, into the central column. Then, ask of each function the following questions:

a. How do I (verb) (noun)? Record the answer(s) in the right column.

b. Why do I (verb) (noun)? Record the answer(s) in the left column.

FIGURE 10.2 Function worksheet for FAST.

3. The diagram layout. Next, write each function separately on a small card in verb – and-noun terminology. Select a card with the function that you consider to be the basic function. Determine the position of the next higher and lower function cards by answering the following logic questions:

a. Perform the “how” test by asking of any function the question, “How do I (verb) (noun)?” The function answer should lie to the immediate right. Every function that has a function to its immediate right should logically answer the “how” test. If it does not, either the function is improperly described or a function is in the wrong place.

b. The second test, “why,” works in the same way, but in the opposite direction. Ask the question “Why do I (verb) (noun)?” The answer should be in the function to the immediate left and should read, “So that I can (verb) (noun).” The answer must make sense and be logical.

4. The critical path. To determine whether a function belongs on the critical path, test the functions with these questions:

a. How is (verb) (noun) actually accomplished, or how is it proposed to be accom­plished?

b. Why must (verb) (noun) be performed?

5. The support logic block. A support logic block is a block immediately underneath a given block at the same general level of activity. This contains functions that “happen at the same time as” and/or “are caused by” some other function. They can be deter­mined by answering these questions:

a. When is (verb) (noun) performed?

b. If (verb) (noun) is performed, what else must also happen?

6. Locating the scope lines. In determining where to place the scope lines, the choice is arbitrary. Actually, moving the left scope line from left to right lowers the level of activity of the problem to be studied. The basic function to be studied shifts, since it is always the function that lies to the immediate right of the left scope line. Locating the right scope line determines the assumptions and “givens” one is willing to accept before starting the study. Location of both scope lines is also subject to the point of view of the owner or user of the problem.

See NCHRP Synthesis 352 for an example of a FAST diagram for a highway application.

Future Performance

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The observation of climate changes, as a consequence of global warming, reveals the aggravation of extreme situations, including alternating torrential rain periods with drought situations. Therefore, it’s important to ensure that road drainage systems are calculated for extraordinary phenomenon (both precipitation and flow) associated with a predetermined return period, which includes an allowance for the worsening of weather conditions. Designing to historic weather patterns is likely to mean that there will be an increase in the frequency when elements of the drainage system will not have adequate capacity, with inevitable consequences for the safety of users and, eventually, for the survival of the infrastructure itself.

Today’s road drainage elements should be monitored to allow measurement of the return period for which they are designed, adopting in latter life of the drainage system a solution for increasing the capacity in face of the reality found on site. One should also ensure that inside this observation phase (which could take some years), efficient cleaning and maintenance plans are implemented with adequate frequency, so that the drainage elements are in perfect functioning order. For example, after drought seasons the tendency to become clogged with sand is higher.

Future infrastructures should be dimensioned by adopting the revised values and parameters collected through information recovered in rainfall and/or water flow monitoring stations placed near the locations of the particular road scheme.

13.5 Conclusion

A safe and comfortable road requires a great investment in scheme planning, careful design, quality construction and ongoing maintenance. At each stage of the road’s life, the hydraulic, geotechnical and pavement performance must be considered alongside the environmental response of the road and its “corridor”.

Drainage standards exist to aid design, performance and maintenance, but they are not to be followed as laws, but as a reference and recommendation for a project. As important as the standards are for many facets of a highway’s design (includ­ing the safety aspects), it is the engineer’s experience and good sense that must determine the road scheme planning and its detailed execution at a project level. Greater rigor by consultants and owners concerning the choice of drainage solutions is important, yet they should be given greater flexibility in the project’s execution schedule and in construction of the work’s drainage system. It is also the consultant and owner who are best placed to determine the appropriate safety implementation.

The wide variety of solutions available to ease the road through the hydraulic en­vironment will necessitate careful study and selection in order that the most econom­ically, socially and environmentally beneficial solution is found. A similar attention will need to be paid to the selection of materials and components. This is partly because of the wide range of geosynthetic materials and composites with proper­ties specifically “tuned” to drainage applications that are now readily available and partly because of the ever-increasing pressure to use marginal, waste and by-product construction materials in place of the conventional aggregates with which designers may be more familiar.

This chapter has, albeit briefly, sought to indicate something of the breadth of solutions and the considerations. It will be apparent that much more could be written and much more detailed design advice and sample calculations could have been pre­sented. However this chapter is already the longest in the book and the book longer than intended! It will suffice for now to advise readers of the wealth of information available in the references listed below and at the end of the previous chapters.

Water is often considered the chief enemy of the pavement engineer. It is one of the materials to which the environmental expert gives prime attention. It is the very basis of the hydrogeologist who seeks to protect it so as to ensure continued pure water supplies. It is right, therefore to make it the subject of this book which, one hopes, will help to ensure that it is treated appropriately by everyone who has a role to play in providing and maintaining roads in our precious environment.

Innovation

Posted by on 26/ 11/ 15

The legacy of Alexander is somewhat mixed insofar as innovation is concerned. To his credit there is the city of Alexandria, with its cultural diversity and intellectual fertility. Of course there is also Archimedes, founder of hydrostatics and supposed inventor of the “Archimedes screw”. There is also Ctesibios, inventor of the fire pump. But other inno­vations never really emerged from their cocoons to find practical application. These include the aeolipile (wind ball) of Heron, a device whose further development could easily have led to the steam engine. There were many other such inventions, and seem­ingly useless gadgets, that were destined to be investigated or rediscovered by Arab sci­entists or, even later, by Leonardo da Vinci and other great thinkers of the Renaissance. Even during the shining period of Alexandria, the greatest innovations seem to have risen from obscurity, from the shadows, from anonymous inventors. The paddle wheel, the water mill, the noria are all born somewhere in the Orient and then progress through history silently, leaving traces of their passage only by chance, here in a description by Strabo, there in a Greek poem…. The windmill is not conceived in the great library of Baghdad but in the Persian countryside. Also in China, nursery of innovation from the 3rd century through the end of the Middle Ages, inventions come from a few obscure civil servants such as Tu Shih, who “loved the common people and wanted to lighten their work”, and to this end brought hydraulic energy to the forges. Or Chiao Wei Ho who invented the lock to avoid damaging boats that had to be dragged from one section of a channel to another. Or such as the anonymous inventor who developed the axial rudder for ships. These innovations did not come from the minds of scholars working in imperial courts.

From the above observation, one has to ask: of what use are teams of scientists and research institutes? Where these existed in ancient times, they were instrumental in the spread and standardization of useful inventions, fostering the rapid refinement and opti­mization of new devices, ensuring that optimal configurations and designs were adopt­ed in practice. The dimensions of the Chinese “dragon backbone machine” were stan­dardized from the 9th century on. Without manuals and other technical documentation, the dissemination of technical innovation is an extremely slow process – errors are repeated, and the “optimal” design develops very slowly. The Roman aqueducts are characterized by surprising conceptual flaws given the experience that could and should have been accumulated. Similarly Roman dams are sometimes well conceived, but just as often are very badly designed. The arch dam seems to have been “re-invented” many times over.

Innovations transcend the boundaries of civilizations. But lacking written traditions, their dissemination and spread is extremely slow. Perhaps the most significant example of this is the spread of the qanat, the device for tapping groundwater that is so simple in principle, if not in application. Conceived in Armenia or in Persia between the 10th and 8th century BC, it is spread into the Orient by the Persians, and is further developed by the Romans who take it to Lybia and Tunisia. But Morocco does not see the qanat until it has made at least two other journeys: one with the westward migration toward the Saharan oases, and another that comes from Muslim Spain to Morocco following the Reconquest.

In the absence of written descriptions, such technical devices tend to be developed differently from one locality to another, reflecting the vicissitudes of oral transmission of know-how rather than the best adaptation of the technology to the local situation. The water mill has a horizontal wheel in the China and the Arab world, but a vertical wheel in the Occident, and the same is true of the windmill at a much later period. The sail rigs on Chinese junks, so perfectly adapted to the needs of coastal commerce in China, do not spread into the West where oarsmen perish in the galleys.

Using Solar for Space Heating

Posted by on 26/ 11/ 15

Solar collectors are commonly used for do­mestic hot water, but they also can supple­ment both forced-air and hydronic heating

systems. In Europe, says Tim Merrigan of the National Renewable Energy Laboratory in Boulder, Colo., package systems that do both are relatively common. But due to heavy winter-heating loads and reduced solar potential, homeowners in this country shouldn’t expect to get much more than one-third of their winter heat from solar sources with today’s technology.

Elia Kleiman, the president of Synepex Energy in Cambridge, Mass., says the pro­portion of winter heat from solar depends on the type of heating system, the amount of insulation installed, and the tightness of the house. A best-case scenario in New England, land of snowy winters and cold, dreary springs, is that a solar system meets 40% to 70% of the heating load. That’s in a well-sealed house with a radiant-floor heat­ing system.

Radiant-floor heating is especially well suited to solar hot-water systems because it requires lower water temperatures, 120°F versus the 180°F that would be pumped through a typical baseboard hydronic sys­tem. Solar hot water also can be used for newer forced-air systems that use a technol­ogy called "hydro air." These boilers heat water forced through a heat-transfer coil, where it warms outgoing air.

For a hypothetical house of roughly 2,500 sq. ft.—well insulated and well sealed—Kleiman says Synepex would prob­ably recommend eight evacuated-tube col­lectors covering roughly 400 sq. ft. of roof. That would provide 100% of domestic hot water in addition to what the system sup­plied to the space-heating side.

Systems like that aren’t cheap. Although it’s difficult to offer meaningful numbers without knowing specifics, Kleiman says that a solar-radiant floor system could eas­ily cost $16,000 and possibly as much as $24,000 before tax credits and rebates. That’s many times more than a system designed for only domestic hot water. If the collectors were tied to a baseboard hot-water system rather than a radiant floor, a homeowner

1

How Much Will My System Cost?

ost is a key consideration when weighing the value would increase by as much as $3,690, merits of renewable energy, not only because the my annual utility savings would be from $224 to systems tend to be expensive, but also because they $335, and I would remove 21 tons of greenhouse force us to think about energy in an entirely different gases from the air. That’s the equivalent of way. A conventional water heater doesn’t cost much, 42,000 auto miles.

but it’s expensive to operate over its lifetime. A solar Years to break even? Between three and four, hot-water system is much more expensive up front but not including the system’s impact on property-value costs less to use. appreciation. If I wanted estimates, a link would Thinking in generalities isn’t helpful when it comes take me to a list of local installers, complete with to deciding whether solar hot water is a reasonable contact information, services offered, and a brief investment. For specifics, I went to www. findsolar summary of their experience.

.com, a website run under the auspices of the Depart – 2. In Tucson, Ariz., where utility rates are lower but the ment of Energy the American Solar Energy sun shines brighter, a similarly sized system would

and the Solar Electric power Association. Its an excel – produce between $252 and $378 in annual utility lent place to get started on a hot-water system and savings

provides a variety of other useful links.

3. In Pensacola, Fla., lower state incentives and utility

A worksheet let me plug in a lot of specifics: my

rates drive the savings down to a range between

state, county, electric utility, and the number of people

$74 and $110.

living in the house. In just a few seconds, the site

came up with the size of the system I’d need, length 4. In Daytor1, Ohia the savings are about Ию same as of payback, annual utility savings, and even return on in Pensacola (about $85 per year). investment. If electricity rates increase more in the future than 1. In southern Maine, I’d need one collector of about now forecast solar hot water wiN become a viable 32 sq. ft. to produce the 35 gal. of hot water my option for more people. Until then, when it comes to wife and I would use in a day. Having the system saving money with solar hot water, rt seems that if you installed would cost about $3,500, but after a have high utility rates, you’d be smart to get a system state rebate and the federal tax credit, the net cost on your roof. If not the decision depends on your com – would be less than half that. Moreover, my property mitment to a cleaner environment.

Map indicates an annual average of daily

kwh/m2/day know* hours per square meter per day solar-radiation potential for a south-facing flat

collector array, mounted at an angle equal to its latitude. Data courtesy of National

4-4.5 4.5-5 5-5.5 5.5-6 6-6.5 6.5 Renewable Energy Laboratory.

Active Systems Reduce Heat Loss

Подпись: Hot water to fixtures Подпись:Подпись: Cooler water settles at bottom of tank and circulates to collector.Using Solar for Space HeatingПодпись: Hot-water storage tank/water heaterПодпись:Подпись:Подпись:Using Solar for Space Heating

Подпись: Photovoltaic panel powers pump; grid current can also be used.

In active systems, electric pumps speed circu­lation to reduce heat loss. As illustrated here, water is run through flat-plate collectors (essen­tially heat collectors plumbed with a network of copper pipe) to the water heater. In areas sub­ject to occasional freezing, an optional valve drains water into a secondary storage tank when its temperature approaches 32°F. The Alternative Energy Store® (http://home. alten ergystore. com) sells an open-loop kit consisting of two large flat-plate collectors, hardware, and pump for about $3,600. Shipping and installa­tion are not included.

Using Solar for Space Heating

might expect to see solar take care of only 20% to 40% of the heating load.

A big drawback of trying to heat a house with solar hot water is that demand is high­est when the heat potential of the system is lowest. On an overcast day in northern New England, the sun is long gone by late afternoon, and the call for heat goes up ac­cordingly. The answer is to store hot water generated during the day in storage tanks so that it can be used for heat when the sun goes down or when the days are cloudy. Tanks can be very large, 2,000 gal. or more, although Kleiman says newer systems can use much smaller tanks that hold as little as 200 gal.

Researchers are also looking down the road at promising new possibilities. Merri – gan, for example, describes one experimen­
tal project in Canada where solar collectors are used to heat the ground when solar potential is abundant in summer. In winter, geothermal heat pumps can be used to ex­tract the stored heat. This seasonal storage of heat is one idea that could make 100% solar heat possible in the future—even in Calgary, Alberta.

WHOLE-HOUSE BACKUPS

Posted by on 26/ 11/ 15

Whole-house backups (where none of the plumbing fixtures drain) indicate either a problem in the building drain, the sewer, or the septic system. There is no way to know where the problem is until some investigative work is done. It’s possible that the problem is associated with the septic tank, but you will have to pinpoint the location where trouble is occurring.

For all the plumbing in a house to back up, there must be some obstruc­tion at a point in the drainage or septic system beyond where the last plumb­ing drain enters the system. Plumbing codes require clean-out plugs along drainage pipes. There should be a clean-out either just inside the foundation wall of a home or just outside the wall. This clean-out location and the access panel of a septic tank are the two places to begin a search for the problem.

If the access cover of the septic system is not buried too deeply, I would start there. But, if extensive digging would be required to expose the cover, I would start with the clean-out at the foundation, hopefully on the outside of the house. Remove the clean-out plug and snake the drain. This will normally clear the stoppage, but you may not know what caused the problem. Habit­ual stoppages point to a problem in the drainage piping or septic tank.

Removing the inspection cover from the inlet area of a septic tank can show you a lot. For example, you may see that the inlet pipe doesn’t have a tee fitting on it and has been jammed into a tank baffle. This could obviously account for some stoppages. Cutting the pipe off and installing the diversion fitting will solve this problem.

Sometimes pipes sink in the ground after they are buried. Pipes some­times become damaged when a trench is backfilled. If a pipe is broken or de­pressed during backfilling, there can be drainage problems. When a pipe sinks in uncompacted earth, the grade of the pipe is altered, and stoppages become more likely. You might be able to see some of these problems from the access hole over the inlet opening of a septic tank.

Подпись:Once you remove the inspection cover of a septic tank, look at the inlet pipe. It should be coming into the tank with a slight downward pitch. If the pipe is pointing upward, it indicates improper grading and a probable cause for stop­pages. If the inlet pipe either doesn’t exist or is partially pulled out of the tank, there’s a very good chance that you have found the cause of your backup.

In the case of a new septic system, a total backup is most likely to be the result of some failure in the piping system between the house and the septic tank. If your problem is occurring during very cold weather, it is possible that the drain pipe has retained water in a low spot and that the water has since frozen. I’ve seen it happen several times in Maine with older homes.

Running a snake from the house to the septic tank will tell you if the prob­lem is in the piping. This is assuming that the snake used is a pretty big one. Little snakes might slip past a blockage that is capable of causing a backup. An electric drain-cleaner with a full-size head is the best tool to use.