Music is cool. Laptop orchestras are even cooler. The sun, on the other hand, is very hot. Bringing these things together might be cool or hot or both. In an age of energy and financial crises, our goal is to create electronic music using sustainable power methods, providing for the possibility not only of conservation and ecology but also of alternative performance sites, including outdoors and other non-traditional locations. Ultimately we strive to develop a sus-tainable power plan for off-the-grid ensemble performances and installations.

Some BackgroundLaptop Orchestras, a Very Brief HistoryThe Princeton Laptop Orchestra (PLOrk) [1], an ensemble of computer-based meta-instruments, was founded in 2005 by Princeton professors Perry Cook and Dan Trueman, with graduate students Scott Smallwood and Ge Wang. The en-semble is composed of undergraduate and graduate students who act as performers, researchers, composers and software developers, exploring ways in which the computer can be in-tegrated into conventional music-making contexts, such as chamber ensembles or jam sessions, while radically transform-ing those contexts and creating new opportunities afforded by technology.

Many other such groups have emerged over the last few years, including the Stanford Laptop Orchestra (SLOrk) (founded by Ge Wang), the Oslo Laptop Orchestra (OLO), The Boulder Laptop Orchestra (BLOrk), the Tokyo Laptop Orchestra, the Moscow Laptop Cyber Orchestra (CybOrk), the Seattle Laptop Orchestra, the Berlin Laptop Orchestra and the Helsinki Computer Orchestra.

For ensembles of this sort, which include anywhere from six to 26 players, the questions of power, amplification and portability are of central concern. In 2008, the Prince-- ton Laptop Orchestra received a John D. and Catharine T. MacAr-thur Foundation Digital Learning Initiative grant to build a “Mobile Music Laboratory.” The main goal of the work under this grant has been to reduce the size and weight of the PLOrkStation instruments, to increase the number of people in the orchestra and to make the instruments (thus the en-semble) more portable. One of our major projects this year has involved the production and deployment of a new hemispheri-cal speaker, with self-amplification and an integrated audio in-terface [2]. This new piece of equipment has not only allowed us to become much more portable due to physical size reduc-tion but has also allowed us to reduce our carbon footprint significantly. Whereas in previous years our gear consumed a maximum of 158 watts per person, this year we have reduced that number to 108. In fact, we can even throw in a subwoofer for each PLOrkStation and still be under the previous year’s power draw (108 + 40 watt sub = 148). While working toward this end (Fig. 1), our existing interests in alternatively powered musical devices caused us to begin thinking about alternative power for PLOrk.

Solar Meditations, Installations and SCrittersAs a precursor to the larger questions about PLOrk and the feasibility of battery and/or solar power, we have investigated the use of solar panels by constructing a variety of light-sensi-tive/powered devices and instruments.

Cook has built several small, intimate solar-charged battery-

©2010 ISAST LEONARDO MUSIC JOURNAL, Vol. 20, pp. 89–95, 2010 89

Perry R. Cook (educator), Departments of Computer Science and Music, Princeton Uni-versity, 35 Olden Street, Princeton, NJ 08540, U.S.A. E-mail: <prc@cs.princeton.edu>.

Scott Smallwood (educator), Department of Music, University of Alberta, 3-82 Fine Arts Building, Edmonton, AL, T6J 4H1, Canada. E-mail: <scott.smallwood@ualberta.ca>.

a B S t r a C t

This paper describes a series of investigations into the use of sustainable methods for power-ing electronic musical instru-ments and perhaps ultimately a large ensemble such as the Princeton Laptop Orchestra, a collection of 15--25 meta-instruments each consisting of a laptop computer, interfacing equipment and a hemispheri-cal speaker. The research discussed includes the develop-ment of instruments specifically designed for solar power, as well as the use of solar panels and/or batteries to power more conventional devices such as computers and amplifiers.

SOLA: Sustainable Orchestras of Laptops and Analog

PerryR.CookandScottSmallwood

Fig. 1. Generation 1 (left) and new (right) PLOrk-Stations. (© Perry Cook and Scott Smallwood)

Fig. 2. PariSphere, Solar Mali Wheel and Bear’s rock Box. (© Perry Cook and Scott Smallwood)

90 CookandSmallwood, SOLA

placement. As an alternative, Feddersen has begun working with high-powered storage capacitors that remove the bat-tery from the equation without sacrific-ing the capacity to smooth, buffer and regulate the fluctuating power of solar panels [5].

Self-described eco-musician Jon Sher-man has performed live with portable solar-powered sound systems since 1988. A fixture in Los Angeles, Sherman per-forms with handmade flutes through his sound system in outdoor festivals and farmers’ markets. His 12-volt system consists of conventional sound gear pow-ered by four 50-watt (Siemens SM50) so-lar panels charging eight 225-Ah (Amp hours capacity) deep-cycle Trojan T-105 batteries through a pair of high-power 120VAC inverters. His gear is installed in a small utility trailer, with the solar array mounted on top [6].

Solar Power and regulationSolar PV panels utilize an array of pho-tovoltaic (PV) cells to convert the sun’s energy into electricity. Arrays of cells are generally organized in series/parallel in order to achieve the desired power. For example, four 3-volt, 40-mA panels in se-ries will yield 12 volts at 40 mA (Fig. 5). Two of them in parallel will yield 12 volts at 80 mA.

Since the sun’s availability is limited, in most applications this electrical en-ergy is stored in batteries. Although it is possible to use the solar panels “raw,” as some of our examples do, it is unwise for most applications, particularly where sensitive computer circuits are involved. A typical system will include an array of solar panels, batteries and a charge con-troller, which contains a voltage regula-tor for keeping the batteries within safe operating ranges, since both overcharge and frequent deep discharges are harm-ful to the life of a battery (Fig. 6). The best systems are shunt regulators, which monitor the battery’s condition and shut off the connection between the panel and the battery if there is excess energy. Even with the best designs, however, a battery’s charge/discharge capabilities are limited, requiring eventual battery replacement.

edu/art/music.html>. When it comes to the use of solar technology for creating real-time interactive installations and/or performances, one early work of interest is Alvin Lucier’s SolarSounderI (1979), a sound installation powered and con-trolled by sunlight, constructed in col-laboration with electronics designer John Fullema.

Recently, many artists and sound mak-ers have begun to utilize solar panels in their work. Doug Repetto’s CircularSpec-trum Analyzer (2008) uses solar energy to power a shortwave radio and two mo-tors. One motor slowly tunes the radio across the 19 MHz spectrum while the other slowly turns seven wooden discs that are engraved into shapes based upon another solar-powered project in collaboration with media artists Hinkis and Lapidus (LoVid). Repetto’s work is installed in the free103point9 Wave Farm sculpture garden in upstate New York [3].

Jeff Feddersen uses solar panels in his EarthSpeaker installations, an ongoing project in which speakers are embed-ded into large sculptures that are pow-ered by solar panels [4]. Feddersen has conducted much of his research and de-velopment at the Eyebeam art and tech-nology center and he also teaches solar arts at the Parsons School of Design in New York. One of Feddersen’s concerns has been with the maintenance of solar-powered installations that are installed for long-term periods. In these situations, batteries would have to be charged and discharged literally thousands of times, which ultimately results in battery fail-ures and the need for regular battery re-

powered sonic objects. In the PariSphere (2000, Fig. 2a), a battery is solar-charged during the day and the device turns on at dark. Motion around the PariSphere causes a short-wave tuner to seek ran-dom stations and play them randomly amongst the six speakers. The S-Mali Wheel (2007, Fig. 2b) is a simple device that runs off a battery charged by a front-mounted solar panel. Closing a switch causes the Tibetan prayer wheel to spin, and a striker excites two Tibetan cym-bals. Brother Bear’s Big Rock Music Box (2005, Fig. 2c) also has a solar charged battery. Opening the front door reveals a motor-driven Big Bear rocking out for adoring fans, flashing LED concert lights and a music box playing John Lennon’s “Imagine.”

Smallwood’s work has involved using solar panels as the sole source of power with no battery buffering or voltage regulation, thus utilizing solar panels as sensors in addition to providing power to the noise-making devices. The Sound Lanterns (2008, Fig. 3) feature insect-like noise-making analog circuits and an 8-Ohm speaker mounted upside down in a large glass jar. With a 5W solar panel generating from 3 to 16 volts, these de-vices change dramatically as available sunlight waxes and wanes.

Growing out of the Sound Lanterns were a series of hand-held “SCritters,” noise instruments utilizing similar analog circuits (Fig. 4). Each of the instruments features different ways of triggering and modifying the sounds, using mostly pho-tocells, body contacts and an attached so-lar panel, which also provides the power source.

related Solar art and Sound Design by OthersHistorically, the sun, planets and cosmos have played inspirational roles for com-posers of music. Others have “sonified” the sun’s radiation to create music, with some examples featured at Stanford’s Solar Center <solar-center.stanford.

Fig. 3. Sound Lanterns. (© Perry Cook and Scott Smallwood)

Fig. 4. SCritters: HiBox, Puck and Caltrop. (© Perry Cook and Scott Smallwood)

CookandSmallwood, SOLA 91

and the laptop, these maximum power draws are worst-case scenarios. Next we will describe some empirical investiga-tions of typical-case scenarios and how they might affect our ability to achieve our goals.

Some results and their ImplicationsIn the case of the hemispherical speaker, the results were quite encouraging. If the hemi were really drawing 48 watts constantly, a 3.4Ah 12-volt seal lead-acid (SLA) battery would be able to power it for less than 1 hour. In practice, how-ever, the average power draw is much less, since all six drivers are not firing constantly. In several test cases, in fact, we have been able to power a hemi for over 12 hours at nominal volume levels. Running the hemi off a 12-volt SLA bat-tery turns out to be a big win. In addition, since no inverter is required to power the hemi, it can be connected directly to the battery.

The laptop itself turns out to be the biggest power hog, but there are several conditions one can take into consider-ation to lessen the power draw. Using two matching 2-GHz Macbooks, we tested how long each laptop could perform under various conditions. The screen turns out to be a big factor, as does the type of visual interface the software uses to display information. We tested battery performance using ChucK to generate six channels of sound, using either (1) an onscreen interface programmed in Processing (which is basically like play-ing a game that uses GL), (2) a “dumb” terminal-based interface (just updating text in the terminal) and (3) no interface (screen dimmed to black). Obviously the results were dramatically improved if no screen were used: Both Macbooks were able to play music continuously for over 4 hours with screens off, even powering a USB interface and operating on six chan-nels, using only their internal batteries (Fig. 7).

Internal battery life can be supple-mented with an external battery, but due

peak). A minimal system for each PLOrk performer includes an Apple laptop powering a multichannel interface (60 watts) and a hemispherical speaker (48 watts). Our hemispherical speakers con-tain three stereo Tripath T-amp (Class D) amplifier modules designed (with our modifications) by diyparadise [7]. These are capable of delivering about 10 audio watts maximum per channel, for a total of 60 watts. A PLOrkStation hemispherical speaker is powered by a 12-volt 4-amp power supply, making its maximum power draw 48 watts.

Apple specifies a maximum continu-ous power rating of 60 watts for a 2-GHz Macbook. The internal battery delivers 45 watt-hours of energy [8]. This means that a Macbook battery is capable of de-livering approximately 2.72 amp-hours (hereafter, Ah), yielding about 1.34 hours of use if the machine is running only off its internal battery at maximum power draw.

For both the hemispherical speaker

Given these parameters, what possibili-ties do these technologies provide for a laptop orchestra?

Toward Solar lapTop orcheSTraSBasic QuestionsIn thinking about sustainable power for PLOrk, which potentially involves power for more than 20 performers, each with a computer, a hemispherical speaker and in some cases a subwoofer, many ques-tions are raised. The most basic questions are:

• What is a minimal system and its current requirements?

• What is our typical system and its current requirements?

• What do we need to power our equip-ment and how long can we expect to perform?

As mentioned above, a single PLOrk-Station consumes about 108 watts (at

3 V40 mA

- +

3 V40 mA

- +

3 V40 mA

- +

3 V40 mA

- +

3 V40 mA

- +

3 V40 mA

- +

3 V40 mA

- +

3 V40 mA

- +

- +12 volts @ 80 mA

Fig. 5. PV panels in series/parallel. (© Perry Cook and Scott Smallwood)

- + - + - +

- +

Charge Controller

>...

110’ 194’ 252’

Fig. 6. PV panel, charge controller, battery, load. (© Perry Cook and Scott Smallwood)

Fig. 7. average laptop internal battery performance. (© Perry Cook and Scott Smallwood)

92 CookandSmallwood, SOLA

power (400+ watt) inverters include loud internal cooling fans that are unaccept-able for musical applications. We have found that powering a laptop with an inverter and a hemispherical speaker off of one battery introduces noise into the audio system. Thus we have found that the ideal situation is to power each unit individually with a quiet low-power in-verter, rather than aggregating the power requirements of the entire system.

3.4-Ah battery in less than 10 hours with no load attached. This is a convoluted process that would be much simpler if computer makers would provide more standardized and transparent means of using alternative DC power sources (for example, Apple forbids third par-ties from making an external battery or adapter because of their proprietary Mag- Lock connector).

We must also point out that many high-

to the proprietary nature of Apple power supplies, a power inverter must be used to convert from direct battery current back to the 120VAC current that the laptop power adapter and subwoofer power sup-ply can deal with. Unfortunately, power inverters waste some energy to convert from DC to AC, while the power supply in the device itself then converts that AC back into DC. For example, we found that our 140-watt inverter will drain a

Fig. 8. Laptop with battery, PV panel and hemispherical speaker with battery. (© Perry Cook and Scott Small-wood)

Fig. 9. two-battery, 85-watt solar panel system. (© Perry Cook and Scott Smallwood)

CookandSmallwood, SOLA 93

power system consisting of two 12-volt SLA batteries (one 3.4 Ah, and one 7 Ah), one 10-watt PV panel, a charge con-troller and one 140–150-watt inverter, at a cost of approximately $250 (currently) per PLOrkStation.

What about just using PV panels to charge the batteries ahead of time? How long does it take to charge the batteries from PV panels? If a PV panel outputs a current of .5 amps, such as our 10-watt PV panel, a 3.4-Ah battery would take al-most 7 hours to charge (3.4/0.5). On the high end, our 85-watt Shell SQ85P panel (see Fig. 9) can charge two 7-Ah 12-volt batteries in about 3 hours (any quicker is bad for the batteries). Using a typical AC battery charger, a 3.4-Ah battery takes about 5.5 hours to charge. A 7-Ah battery takes almost 13 hours.

Thus, it is not hopeless. In fact, even without the PV panels present, we can certainly mount a laptop orchestra con-cert without the use of the electrical grid, provided we have a healthy fleet of fully charged batteries and are smart about the design of visual interfaces and the use of the laptop screen. Recently we, performing as the Battery Laptop Broth-ers (BLaB) (Fig. 10), played a 10-min-ute duet improvisation in concert (time limited by concert programming, not battery life), with four battery-powered laptops, four battery-powered hemis and several battery-powered instruments.

for each of the two batteries. Obviously, large solar panels are too unwieldy for this kind of application. Our 10-watt PV panel is about twice the size of a laptop, making it reasonably portable.

Since the hemispherical speaker al-ready lasts for well over 10 hours of continuous operation with one battery, supplementing it with a solar panel is perhaps unnecessary, but doing so would increase the amount of time significantly, insofar as sunlight is available. In fact, we have been able to power a hemi directly with the 10-watt PV panel with no battery using a 7812 regulator to keep the voltage at 12 volts. Obviously the speaker cannot be turned up very loud in this case, as it begins to distort at higher levels. This could be alleviated somewhat with the ad-dition of a large storage capacitor (or of course a battery). Using a battery ensures that concert-level audio can be obtained, and adding a PV panel becomes super-fluous for a concert situation but quite advantageous for all-day operation.

In the case of the laptop, adding a 10-watt solar panel can significantly increase performance time. In our tests, we found that a laptop powered by a 7-Ah battery connected to the PV panel through a charge controller yields an extra 30–45 minutes of operation, depending on available sunlight, screen usage and other factors.

The system in Fig. 8 shows a practical

In our tests with external batteries, we have been able to power a laptop for 20–30 minutes beyond internal battery life with a single 3.4-Ah SLA battery and a 140-watt inverter using an active inter-face. This increased to almost 2 hours with a 7-Ah battery using the same in-verter. Why such a huge difference? SLA batteries are rated assuming a slower dis-charge rate. If, for example, a battery is discharged in only 1 hour, its capacity will fall sharply (usually about half). There-fore, given the power draw of the laptop, we would need to use a larger capacity battery. Given our initial primary goals of smaller, lighter and more portable laptop orchestras, this doesn’t look too encouraging.

So Is It Hopeless?Given the size and power specifica-tions of PV panels, how practical is it to use them to supplement the power re-quirements of a laptop orchestra? We have seen from our tests above that a minimal PLOrkStation consisting of a hemispherical speaker powered from a 3.4-Ah 12-volt battery and a Macbook with a healthy, fully charged internal bat-tery supplemented with an external 3.4- or 7-Ah 12-volt battery can play music from anywhere between 2 and 6 hours, depending on the use of the computer screen and perhaps other variables (such as reading sound files off the hard drive). This is plenty long enough for a concert. Could adding solar panels give us signif-icantly more time? Indeed they would, but at what cost and size?

In order to provide significant extra power, each player would presumably need a minimum of two solar panels, one

Fig. 10. BLaB: (left) Skot&Caltrop, (right) Perry&Maggie. (© Perry Cook and Scott Smallwood)

94 CookandSmallwood, SOLA

ence has underlined the need for more reasonable power options for laptop computers through the potential coop-eration of manufacturers of computing technologies to eliminate proprietary power supplies and provide/incorporate mechanisms that enable and encourage alternative energy sources. For example, the One Laptop per Child project [11] has created small wireless systems that include solar-charged batteries. If laptop manufacturers agreed upon a standard power specification that could easily be adapted for alternative energy systems, this would go a long way toward sustain-able practices. We personally would vote for a 12-volt DC supply via a standard barrel connector (N- or M-type), thus enabling a wide variety of standard bat-teries and power supplies to interoperate with computers.

In summary, we hope that not too long from now, we can conduct an en-tire performance with 20–25 players of full-spectrum music completely off the grid, opening up opportunities for per-formances in interesting and remote locations.

references

1. D. Trueman, “Why a Laptop Orchestra?” OrganisedSound 12(2), (2007) pp. 171–179.

2. S. Smallwood, P. Cook, D. Trueman, “Don’t Forget the Laptop: A History of Hemispherical Speakers at

and often quirky solar-charged/excited instruments have already yielded much fruit for live performances and installa-tions, and we look forward to crafting more of these instruments. And thanks to the use of new amplification technolo-gies such as Class-D amplifiers, we have been able to vastly reduce the power requirement for sound reinforcement. Finally, through explorations of musical instruments that do not require visual onscreen feedback, we have been able to significantly minimize the amount of power required to power our laptops.

As for future work, we hope to find efficient means of powering subwoof-ers to supplement our sound, since our hemis roll off at about 80 Hz. In our normal concerts, we routinely include subwoofers for each player. Our current subwoofer of choice is the Yamaha YST-FSW050BL, which has a power draw of 40 watts at 120VAC, about 3.3 amps. Again this is peak worst-case, and both orches-tra and audience would suffer greatly if we played this loud continuously. In prac-tice, we were able to achieve about 1 hour of performance from a subwoofer pow-ered from a 3.2-Ah battery with a 140-watt inverter playing relatively sub-heavy mu-sic. However, perhaps a new subwoofer design would improve this situation in the future.

We should mention that this experi-

Finally and importantly, it is certainly possible to design instruments that do not require visual feedback onscreen, thus saving the energy required to power them. For example, Fig. 11 shows an installation using two laptops, two bat-tery-powered hemis and two small solar-powered interfaces that also generate sound. Moving the small devices around causes changes in their sound, which in turn affect the way the laptops process that sound. No visual interface is used; instead, players simply use their ears to perform. This piece lasted for almost 4 hours before one of the laptops’ batteries gave out.

concluSionS and FuTure workSolar PV technologies are finally becom-ing more cost effective and technologi-cally efficient, with prices for materials decreasing from $25 per watt to less than $3.50 per watt, an 86% reduction [9]. In addition, some recent innovations have promised a significant increase in the efficiency of solar panels to collect sunlight through the application of new antireflective coatings that increase the amount of sunlight captured by solar panels regardless of the angle of those panels with respect to the sun [10].

Our experiences with small, personal

Fig. 11. Example solar/laptop battery installation. (© Perry Cook and Scott Small-wood)

CookandSmallwood, SOLA 95

DigitalLearning Initiativegrant in2009.Cookisalsoafoundingadvisor/consultantto iPhonemusicAppcompanySonicMule.

ScottSmallwoodisasoundartist,composerand sound performer who creates worksinspired by discovered textures and forms,throughapracticeof listening,fieldrecord-ingandsonicimprovisation.Healsodesignsexperimentalelectronicinstrumentsandsoft-ware,aswellassoundinstallationsandsite-specific performance scenarios. He receivedhis Ph.D. in composition from PrincetonUniversity,whereheworkedwithPerryCookand Dan Trueman to found the PrincetonLaptopOrchestra (PLOrk).Heperformsasone-halfofthelaptop/electronicduoEvidence(withStephanMoore)andcurrentlylivesinEdmonton,Alberta,whereheteachescomposi-tion,improvisationandelectroacousticmusicattheUniversityofAlberta.

10. M. Kuo, D. Poxson, Y. Kim, F. Mont, J. Kim, E. Schubert, and S. Lin. “Realization of a Near-Perfect Antireflection Coating for Silicon Solar Energy Utili-zation,” OpticsLetters33 (2008) pp. 2527–2529.

11. One Laptop Per Child (OLPC), <www.laptop.org>.

Manuscript received 1 January 2010.

PerryR.CookreceivedaB.A.inMusicandB.S.inEEfromtheUniversityofMissouriatKansasCityConservatoryandUMKCSchoolofEngineeringin1984and1985.HeearnedhisEEPh.D.atStanfordCCRMAin1990,continuingasTechnicalDirectorofCCRMAthereafter.HejoinedPrincetonUniversityin1996asProfessorofComputerScience,found-ingthePrincetonSoundLab.CookreceivedaGuggenheimFellowshipin2003,andfoundedthePrincetonLaptopOrchestra(PLOrk)withDanTrueman.PLOrkreceivedaMacArthur

Princeton, Plus a DIY Guide,” Proceedingsofthe2009NewInstrumentsforMusicalExpressionConference, Pitts-burgh (2009).

3. D. Repetto, CircularSpectrumAnalyzer.See <music.columbia.edu/~douglas/portfolio/CSA/>.

4. J. Feddersen, EarthSpeaker, <fddrsn.net/video/esAcra.html>.

5. J. Feddersen, “The making of Jeff Feddersen’s EarthSpeaker,” (podcast) Eyebeam, July 5, 2006, <www.eyebeam.org/reblog/journal/podcasts/JeffH.264_300Kbps.mov>.

6. T. Guinyard, “Interview of Jon Sherman,” LifeandTimes, KCET TV, Los Angeles, 25 July 2003. See <www.dryadflutes.com/solarsound.htm>.

7. See <diyparadise.com/charlize.html>.

8. See <www.apple.com/macbook/specs.html>.

9. T. Bradford, SolarRevolution:TheEconomicTrans-formationoftheGlobalEnergyIndustry (MA: MIT Press, 2006).

Nanotechnology, Nanoscale Science and Art

Leonardo Special SectionGuest Editor: Tami I. Spector

2011 is the International Year of Chemistry! To celebrate, Leonardo is seeking to publish papers and art-works that involve the intersections of chemistry, nanotechnology and art for our on-going special section “Nanotechnology, Nanoscale Science and Art.”

Since its inception, nanotech/science has been intimately connected to chemistry; fullerenes, nanoputians, molecular machines, nano-inorganics and self-assembling molecular systems, all spring from the minds and labs of chemists, biochemists and chemical engineers. If you’re a nano-oriented chemist who is serious about art, an artist working at the molecular level, or a chemical educator exploring the mysteries of the nano world through the arts we are especially seeking submissions from you.

Published Leonardo articles that explore the intersections of nanotech/science and art include: “Nanoscale and Painting” by artist Filipe rocha da Silva, “Fact and Fantasy in Nanotech Imagery” by scien-tist David S. Goodsell, and “Midas: A Nanotechnological Exploration of Touch” by artist Paul thomas.

Interested artists and authors are invited to send proposals, queries and/or manuscripts to the Leonardo editorial office: Leonardo, 211 Sutter St., Suite 501, San Francisco, CA 94108, U.S.A. E-mail: <leonardomanuscripts@gmail.com>.

CALL FOR PAPERS